JPH05141344A - Multistage compressor - Google Patents

Abstract

PURPOSE:To uniformize wear of a piston ring and to improve durability by forming a passage, opened in a piston, within a range of the recessed groove of a piston in a cylinder on the high pressure side with which the lower surface of the first piston ring is brought into contact. CONSTITUTION:When a cylinder 1 on the high pressure side is transferred from a re-expansion stroke to a suction stroke, the upper part pressure of a first piston ring 4 is decreased to a value lower than the lower part pressure thereof, thereby the first ring 4 is pushed up once. Gas in a first ring lower chamber flows through a passage 11 and the inside of a piston 2 and rapidly flows in a crank chamber 1b. Thereby, a pressure in the first ring lower chamber is rapidly decreased. In this case, the first ring 4 is pressed by an upper gas pressure and rapidly lowered and brought into adhesion to the lower surface of a recessed groove 3. Further, since, in a second piston ring 5 also, the upper pressure thereof is higher than the lower pressure thereof, the second piston ring is brought into adhesion to the lower surface of the recessed groove 3 and a back pressure is exerted and forced into adhesion to the inner surface of a cylinder. Thus, a differential pressure between the upper and lower parts of the first ring 4 during each stroke is approximately equal to that between the upper and lower parts of the second ring 5 and reduced to the minimum and wear of the rings may be minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention ensures the sealability of the first and second piston rings during the compression stroke in the high-pressure side cylinder of a multi-stage compressor, and prevents the wear of these first and second piston rings. The present invention relates to a substantially uniform multistage compressor.

[0002]

2. Description of the Related Art As a prior art of a seal structure for a piston, one disclosed in Japanese Utility Model Publication No. 1-7888 is known. In this type of technology, when generating air of a desired pressure, the pressure in the first stage cylinder on the low pressure side is set to be lower than the target pressure, and the desired pressure is set in the second stage cylinder on the high pressure side, Like a so-called two-stage compressor, it is used in a multi-stage compressor that has a low-pressure side compression unit and a high-pressure side compression unit and that gradually increases air pressure from the low-pressure side compression unit to the high-pressure side compression unit. In such a multi-stage compressor, FIG.
As shown in FIG. 3, a crankshaft (not shown) provided in the crank chamber 1b is connected via a connecting rod 2a and a piston pin 2b, and is movably provided in the high pressure side cylinder 1 of the high pressure side compression unit. A compression chamber 1a is formed inside the high pressure side cylinder 1 by the piston 2. Further, in order to seal between the compression chamber 1a and the crank chamber 1b of the high pressure side cylinder 1, the piston 2 in the high pressure side cylinder 1 is sealed.
On the outer peripheral surface of the piston 2 in the axial direction of the piston 2 and in the plurality of annular recessed grooves 3, 3 which are sequentially formed from the head of the piston 2 toward the crank chamber 1b side. A piston ring 5 is mounted, and the first piston ring 4 and the second piston ring 5 seal between the compression chamber 1a and the crank chamber 1b. Then, in order to absorb the effects of thermal expansion of the first piston ring 4 and the second piston ring 5 during operation and wear of the first piston ring 4 and the second piston ring 5, these first piston ring 4 and the second piston ring 5 are absorbed. The ring 5 is provided with a joint (abutment), and an appropriate gap is provided at this joint. Reference numeral 6 is a rider ring made of ethylene resin which is fitted on the outer periphery of the piston 2 and serves as a sliding portion of the piston 2.

By the way, in the above prior art, (1) the first piston ring 4 and the second piston ring 5 were the same piston ring. (2) In the high-pressure side cylinder of the two-stage compressor, the internal pressure of the cylinder 1 changes as shown in FIG. 9 (note that P0≈
Atmospheric pressure, P1≈ (P2-P0) / 2, P2 = intermediate pressure, P3≈
(P4-P2) / 2 + P2, P4 = discharge pressure. ). In the re-expansion process A shown in FIG. 9, as shown in FIG. 10, the upper pressure (front pressure) of the first piston ring 4 is the maximum P.
4, the lower pressure (post-pressure) of the first piston ring 4 is slightly smaller than P4 due to the gas leakage between the first piston ring 4 and the inner wall surface of the cylinder 1, and the upper pressure of the second piston ring 5 is Slightly smaller than P4, the lower pressure of the second piston ring 5 becomes P0, and back pressure is applied to the first piston ring 4 and the second piston ring 5, respectively. The sealing function between the pistons 2 is exhibited. In the suction step B shown in FIG. 9, as shown in FIG. 11, the upper pressure of the first piston ring 4 becomes P2, the lower pressure of the first piston ring 4 becomes P2, and the first piston ring 4 becomes free. .. The upper pressure of the second piston ring 5 is P2,
The lower pressure of the second piston ring 5 becomes P0, and due to the pressure difference between the intermediate pressure P2 and the atmospheric pressure P0, the second piston ring 5
A back pressure is applied to the second piston ring 5, and a sealing function between the cylinder 1 and the piston 2 is exerted. In the compression step C shown in FIG. 9, as shown in FIG. 12, the upper pressure of the first piston ring 4 is maximum P4 (discharge pressure), and the lower pressure of the first piston ring 4 is the first piston ring 4.
P4 due to gas leakage between the cylinder and the inner wall surface of the cylinder 1.
It is slightly lower, the upper pressure of the second piston ring 5 is slightly lower than P4, the lower pressure of the second piston ring 5 is P0, and the differential pressure between the discharge pressure P4 and the pressure slightly lower than the discharge pressure P4, respectively. The back pressure is applied to the first piston ring 4 and the second piston ring 5 due to the pressure difference between the discharge pressure P4 and the atmospheric pressure P0, and the cylinder 1 and the piston are formed by the first piston ring 4 and the second piston ring 5. The sealing function between the two is demonstrated. In addition, D in FIG. 9 shows a discharge process. The discharge stroke D is the same as the compression stroke C.

[0004]

However, in the conventional multi-stage compressor described above, the second piston ring 5 is constantly subjected to back pressure during one cycle of operation of the piston 2 in the high pressure side cylinder 1 to receive the back pressure. It is pressed against the inside,
The back pressure also changes from the intermediate pressure P2 to a pressure slightly lower than the maximum discharge pressure P4, but the first piston ring 4 becomes free in the suction stroke B, and the upper pressure and the lower pressure of the first piston ring 4 become Since the differential pressure of the second piston ring 5 is smaller than the differential pressure between the upper pressure and the lower pressure of the second piston ring 5, the back pressure applied to the second piston ring 5 is larger than the back pressure applied to the first piston ring 4. Therefore, there is a problem that the wear amount of the second piston ring 5 is about twice as much as the wear amount of the first piston ring 4.

The present invention has been made in consideration of the above circumstances, and uniformizes the wear of the first and second piston rings while maintaining the sealability of the piston ring in the high pressure side cylinder of the high pressure side compression section. An object of the present invention is to provide a multistage compressor having improved durability.

[0006]

In order to achieve the above object, the present invention has a low pressure side compression section and a high pressure side compression section, and at least the high pressure side compression section is provided in a high pressure side cylinder and a crank chamber. A piston provided movably inside the high-pressure side cylinder to form a compression chamber in the high-pressure side cylinder and a compression chamber of the high-pressure side cylinder. Therefore, the first piston ring and the second piston mounted on the outer peripheral surface of the piston in the high-pressure side cylinder are provided in the groove formed at intervals in the axial direction of the piston and sequentially formed from the piston head toward the crank chamber side. A multi-stage compressor comprising a piston ring and gradually increasing air pressure from a low pressure side compression part to a high pressure side compression part, wherein the first piston of the concave groove of the piston in the high pressure side cylinder is A series of openings formed on the wall against which the lower surface of the ton ring contacts so that one end opens within the range where the lower surface of the first piston ring contacts during the compression stroke and the other end opens into the piston in the high-pressure side cylinder. The outer peripheral surface of the piston in the high pressure side cylinder through the passage of
The space defined between the piston ring, the second piston ring, and the inner wall of the high-pressure cylinder is communicated with the crank chamber.

[0007]

According to the above construction, in the re-expansion stroke A in the high pressure side cylinder, the space defined between the outer peripheral surface of the piston in the high pressure side cylinder, the first piston ring, the second piston ring and the inner wall of the cylinder ( Hereinafter, the gas in the lower chamber of the first piston ring) cannot pass through the passage formed in the wall with which the lower surface of the first piston ring of the concave groove abuts. Therefore, the first piston ring and the second piston ring are brought into close contact with the lower surface of the groove by the action of their upper pressure, and are also brought into close contact with the inner surface of the cylinder by receiving back pressure. During the transition from the re-expansion stroke to the suction stroke, the upper pressure of the first piston ring falls below the lower pressure, so the first piston ring is pushed up once. Once the first piston ring is pushed up, the gas in the first piston ring lower chamber rapidly flows into the crank chamber through the passage and the piston. Therefore, the pressure in the lower chamber of the first piston ring drops sharply. Thereupon, the first piston ring is pushed by the gas pressure above it and immediately descends to come into close contact with the lower surface of the concave groove and also with the back pressure to come into close contact with the inner surface of the cylinder. Further, since the upper pressure of the second piston ring is higher than the lower pressure, the second piston ring adheres to the lower surface of the groove 3 and receives back pressure to adhere to the inner surface of the cylinder. In the suction stroke, the upper pressure of the first piston ring becomes an intermediate pressure, the lower pressure of the first piston ring and the upper pressure of the second piston ring become a pressure higher than atmospheric pressure and lower than the intermediate pressure, and a lower pressure of the second piston ring. Since the pressure is atmospheric pressure,
The piston ring and the second piston ring are brought into close contact with the lower surface of the groove by the action of the upper pressure thereof, and are also brought into close contact with the inner surface of the cylinder by receiving back pressure. Also, the compression process C
Since the one end opening of the passage is closed by the first piston ring, the first piston ring and the second piston ring are brought into close contact with the lower surface of the concave groove by the action of the upper pressures of the first piston ring and the back side pressure of the cylinder. Stick to the inner surface.
Further, the discharge process is the same as the compression process.

As described above, the first piston ring and the passage serve as a valve that connects and disconnects the first piston ring lower chamber and the crank chamber, which makes it possible to increase the inner diameter of the passage and thereby re-expand. During the transition from the stroke to the suction stroke, the pressure in the lower chamber of the first piston ring is sharply reduced, and the back pressure applied to the second piston ring is reduced.
The pressing force of the second piston ring on the inner wall of the cylinder is reduced. Therefore, the pressure difference between the upper pressure and the lower pressure of the first piston ring in each stroke becomes substantially equal to the pressure difference between the upper pressure and the lower pressure of the second piston ring, and the difference between the first piston ring and the second piston ring While maintaining the seal between the cylinder and piston, the first piston ring and the second piston ring
It is possible to make the upper and lower differential pressures of the piston ring substantially minimum in each stroke, thereby making the wear of the first piston ring and the second piston ring substantially uniform, and improving the durability of the compressor.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the present embodiment, the same parts as those in the conventional example are designated by the same reference numerals, and the description of part of them will be omitted. FIG. 1 is a two-stage compressor that has a low-pressure side compression unit and a high-pressure side compression unit, and is an example of a multi-stage compressor that gradually increases the air pressure from the low-pressure side compression unit to the high-pressure side compression unit. This two-stage compressor is the first part of the low pressure side compression section.
The air sucked into the low-pressure side cylinder 1'of the stage is boosted to a pressure lower than the target air pressure by the piston 2'in the low-pressure side cylinder 1'connected to the crankshaft of the crank chamber 1b, and this air pressure is increased. Through the intermediate pipe 7 and sucked into the high pressure side cylinder 1 of the second stage of the high pressure side compression section,
The air sucked into the high pressure side cylinder 1 of the second stage is pressurized to a target air pressure by the piston 2 in the high pressure side cylinder 1 connected to the crankshaft. In addition, 2a 'and 2b' show the connecting rod and the piston pin of the low pressure side compression part, respectively. In the present embodiment, it is possible to make the upper and lower differential pressures of the first piston ring 4 and the second piston ring 5 in each stroke of the piston 2 to be substantially minimum, whereby the first piston ring 4, the second piston 5 While maintaining the sealing property of the ring 5, the wear of the first piston ring 4 and the second piston ring 5 is made uniform.

In FIG. 2, reference numeral 4 is a first piston ring, and reference numeral 5 is a second piston ring. The first piston ring 4 and the second piston ring 5 are made of a sealing material having a non-metal heat resistance elasticity such as ethylene resin which is flexible and highly adaptable, and serves as a gas seal between a cylinder of a compressor and a piston. Is what is used. As shown in FIG. 4, the first piston ring 4 and the second piston ring 5 are made of a sealing material having a non-metallic heat resistant elasticity such as a flexible and highly adaptable tetrafluoroethylene resin. , Both ends of the second piston ring 5 on the compression chamber side of the cylinder, that is, the pressurizing side and the non-pressurizing chamber side of the cylinder, that is, the clang chamber side, are axially stepped and overlap each other in the circumferential direction. In the non-pressurizing chamber-side abutment 13, one end is provided with a notch on the inner peripheral side and a first protrusion 14 is provided on the outer peripheral side, and the other end is provided with a first protrusion from the other end. Of the abutment portion, the booklet, which extends along the inner peripheral side of the protruding portion 14 and is sufficiently flexible to be pressed against the inner peripheral side surface of the first protruding portion 14 by back pressure so as to seal the abutting portion 13. In the specific example, the thickness is greater than the thickness of the first protrusion 14 in the radial direction. It is provided with a second projection 15 having a thin thickness. That is, one end of each of the first and second piston rings 4, 5 has a first protrusion 14 formed on the non-pressurizing chamber side and a notch on the inner peripheral side thereof, and the non-pressurizing chamber. A side portion having a full width W in the radial direction of the piston 2 is formed by cutting out from the tip 22 of the first protrusion 14 to the tip 23 of one end along the circumferential direction of the piston 2. And a first pace portion 21.
The other ends of the piston rings 4 and 5 are connected to the first protrusion 1
A second protruding portion 15 formed by cutting out the outer peripheral side so as to be arranged in a cutout portion 24 on the inner peripheral side of 4;
The piston 2 is in air-tight contact with the first pace portion 21 located in the region of the full width W in the radial direction, and extends from the base 25 of the second protrusion 15 to the one end along the circumferential direction. A second pace portion 20 that continuously extends to a tip 23 of the portion. The second protrusion 15 forms a seal portion between the inner side surface 26 of the first protrusion 14 and the outer side surface 27 of the second protrusion 15 by the back pressure from the compression chamber. In order to be pressed against the side surface 26 on the inner peripheral side of the first protrusion 14, the thickness is formed sufficiently smaller than the thickness of the first protrusion 14 in the radial direction. The piston 2 has a cylindrical shape with one end (upper end in FIG. 2) closed, and is slidably fitted inside the cylinder 1 via a rider ring 6, and the space inside the cylinder 1 is the piston 2
Are divided into a compression chamber 1a and a crank chamber 1b, respectively.

The annular concave grooves 3, 3 are formed on the outer peripheral surface of the piston 2 at intervals in the axial direction of the piston 2 and are sequentially formed from the head of the piston 2 toward the crank chamber 1b. Piston ring 4, second piston ring 5
Has been inserted. The wall 3a of the groove 3 where the lower surface of the first piston ring 4 abuts has an upper groove 3 and the crank chamber 1
The passage 11 is formed so as to be able to communicate with b. The passage 11 is formed in the wall 3a and the outer peripheral wall of the piston 2, and one end of the passage 11 is opened within a range in which the lower surface 4a of the first piston ring 4 abuts the wall 3a during the compression stroke.
The other end is a continuous hole having an L-shaped cross section, which is opened in the piston 2. The passage 11 cooperates with the first piston ring 4 to define a space defined between the outer peripheral surface of the piston 2, the first piston ring 4, the second piston ring 5 and the inner wall of the cylinder 1, that is, the first piston. The lower ring chamber and the crank chamber 1b can be communicated with each other and cut off from each other.

Next, the operation of the two-stage compressor having the above construction will be described. Drive the drive source (not shown) of the two-stage compressor,
Rotate the crankshaft (not shown). Then, the piston 2'is connected to the connecting rod 2a 'and the piston pin 2b in the low pressure side cylinder 1'of the first stage of the low pressure side compression unit.
2 is slid in a substantially axial direction of the piston 2 ', and the piston 2 moves up and down in FIG. 2 via the connecting rod 2a and the piston pin 2b (in the high pressure side cylinder 1 of the high pressure side compression portion). Slide in the direction). Then, the low-pressure side compression unit increases the pressure to a pressure lower than the target air pressure, and the high-pressure side compression unit increases the pressure to a desired pressure.

Here, the inside of the high-pressure side cylinder 1 is moved to the piston 2
Moves downward from the top dead center, that is, in the re-expansion process A shown in FIG. 9, the gas remaining in the clearance volume above the piston 2 expands to the suction pressure due to the lowering of the piston 2, and a new Since gas is sucked in, the upper pressure of the first piston ring 4 is a maximum discharge pressure P4, as shown in FIG. 3, and as the suction stroke approaches, the upper pressure P4 of the first piston ring 4 gradually becomes an intermediate value. Pressure P2
To decline. The lower pressure of the first piston ring 4 is
Since the first piston ring 4 closes the one end opening of the passage 11, the gas in the lower chamber of the first piston ring cannot pass through the passage 11, so that the gap between the first piston ring 4 and the inner wall surface of the cylinder 1 is reduced. The pressure becomes P3 due to the gas leakage. Therefore, the first piston ring 4 has an upper pressure P
By the action of 4, it comes into close contact with the lower surface of the concave groove 3 in FIG. 3 and receives back pressure to come into close contact with the inner surface of the cylinder 1. At this time, the upper pressure of the second piston ring 5 is P3, and the lower pressure of the second piston ring 5 is almost the same as the crank chamber pressure.
0 ≈ atmospheric pressure. Therefore, the second piston ring 5 is acted on by the upper pressure P3 of the second piston ring 5 to cause the concave groove 3 in FIGS.
And the inner surface of the cylinder 1 by receiving back pressure.

When the piston 2 further descends, the re-expansion stroke A shifts to the suction stroke B shown in FIG. 9, during which the upper pressure of the first piston ring 4 changes from P4 to the intermediate pressure P2 shown in FIG. When the upper pressure of the first piston ring 4 falls below P3 during the transition from the re-expansion stroke A to the suction stroke B, the lower pressure of the first piston ring 4 was P3 during the re-expansion stroke A. As shown in 5, the first piston ring 4 is once pushed up. Once the first piston ring 4 is pushed up, the pressure P0 in the crank chamber 1b is lower than the upper pressure P2 of the first piston ring 4, so that the gas in the lower chamber of the first piston ring is in the passage 11 and the piston 2. Rapidly through the crankcase 1
flow into b. For this reason, the pressure in the lower chamber of the first piston ring rapidly drops to a pressure lower than the upper pressure P2 of the first piston ring 4 and higher than the atmospheric pressure P0. Therefore,
The first piston ring 4 is once pushed up and then immediately pushed down by the gas pressure P2 at its upper part and descends, and comes into close contact with the lower surface of the concave groove 3 in FIG.
Adheres to the inner surface of.

As described above, the upper pressure of the second piston ring 5 is P3 until the first piston ring 4 is once pushed up, and thereafter is lower than P2 and lower than the atmospheric pressure P.
Since the pressure is higher than 0 and the lower pressure of the second piston ring 5 is the atmospheric pressure P0, the second piston ring 5 is
The upper groove pressure P3 is maintained until the first piston ring 4 is once pushed up, and thereafter, by the gas pressure lower than the upper pressure P2 and higher than the atmospheric pressure P0, the concave groove 3 in FIG.
And the inner surface of the cylinder 1 by receiving back pressure. When the piston 2 slightly descends when the re-expansion stroke A shifts to the suction stroke B, the gas pressure in the compression chamber 1a tends to decrease sharply due to the small stroke of the piston 2 descending (the piston 2 descends). Since the cross-sectional area of the piston 2 with respect to the stroke is relatively large), when the piston 2 descends a little, the gas pressure in the compression chamber 1a approaches P2 and before the upper pressure of the first piston ring 4 becomes P2, that is, Before the suction stroke B, the first
The piston ring 4 is pushed up from the lower surface of the groove 3.

As described above, from the re-expansion stroke A to the suction stroke B, the upper pressure of the second piston ring 5 is maintained at P3 or the gas pressure lower than P2 and higher than atmospheric pressure, and the first piston ring Once 4 is pushed up, as described above, the lower chamber of the first piston ring immediately drops to approximately P1, and the pressure difference between the upper and lower sides of the second piston ring 5 becomes smaller.
The pressure difference between the upper pressure and the lower pressure of the second piston ring 5 becomes substantially equal to the pressure difference between the upper pressure and the lower pressure of the second piston ring 5, and the second piston ring 5 maintains the sealing property with the cylinder 1. Therefore, the wear amount can be reduced as compared with the conventional one.

In the suction stroke B, the upper pressure of the first piston ring 4 becomes the intermediate pressure P2, and the first piston ring 4
Due to the gas leakage between the first piston ring 4 and the inner wall surface of the cylinder 1, the lower pressure becomes a pressure higher than the atmospheric pressure P0 and lower than the intermediate pressure P2, that is, a pressure close to the pressure P1. The first piston ring 4 has an upper pressure P
By the action of 2, it adheres to the lower surface of the groove 3 in FIG. 6 and receives back pressure to adhere to the inner surface of the cylinder 1. Also,
The upper pressure of the second piston ring 5 is a pressure close to P1 which is higher than the atmospheric pressure P0 and lower than the intermediate pressure P2, and the lower pressure of the second piston ring 5 is the atmospheric pressure P0. Due to the action of the upper pressure, FIG.
It comes into close contact with the lower surface of the recessed groove 3 in FIG.

Further, in the compression stroke C, as shown in FIG. 7, since one end opening of the passage 11 is closed by the first piston ring 4, the upper pressure of the first piston ring 4 is P4 (discharging pressure) at maximum. ), And the lower pressure of the first piston ring 4 becomes P3 due to gas leakage between the first piston ring 4 and the inner wall surface of the cylinder 1. Therefore, the first piston ring 4 comes into close contact with the lower surface of the concave groove 3 in FIG. 7 by the action of the upper gas pressure P4 thereof, and also receives the back pressure and comes into close contact with the inner surface of the cylinder 1. The upper pressure of the second piston ring 5 is P3, and the lower pressure of the second piston ring 5 is P0.apprxeq.atmospheric pressure. Therefore, the second piston ring 5 is moved by the action of the upper gas pressure P3 thereof as shown in FIG.
It comes into close contact with the lower surface of the recessed groove 3 in FIG. As described above, in the compression stroke, the first piston ring 4 not only seals between the cylinder 1 and the piston 2, but also the second piston ring 5
The upper part of the pressure is maintained at P3 and the second piston ring 5 also maintains the sealing property between the cylinder 1 and the piston 2.

In the discharge stroke D shown in FIG. 9, the vertical pressures of the first piston ring 4 and the second piston ring 5 are the same as those in the compression stroke. However, the changes in the vertical pressure values of the first piston ring 4 and the second piston ring 5 in each of the above strokes are changed by the gas sealing performance of the first piston ring 4 and the second piston ring 5 and the fluid resistance of the passage 11, And it depends on the piston speed (the number of revolutions of the crankshaft).

As described above, according to the present embodiment, since the first piston ring 4 and the passage 11 serve as a valve for connecting and disconnecting the first piston ring lower chamber and the crank chamber 1b, the inner diameter of the passage 11 is reduced. Can be increased, whereby the pressure in the first piston ring lower chamber can be sharply reduced during the transition from the re-expansion stroke to the suction stroke, and the back pressure applied to the second piston ring 5 can be reduced, The pressing force of the second piston ring 5 on the inner wall of the cylinder 1 can be reduced. Therefore, the differential pressure between the upper pressure and the lower pressure of the first piston ring 4 in each stroke is
Since the pressure difference between the upper pressure and the lower pressure of the second piston ring 5 becomes substantially equal, the back pressure applied to the first piston ring 4 and the back pressure applied to the second piston ring 5 become substantially equal, and the first piston ring 4, while maintaining the sealing property between the cylinder 1 and the piston 2 due to the action of the second piston ring 5, the respective vertical differential pressures of the first piston ring 4 and the second piston ring 5 can be made substantially minimum in each stroke. As a result, the wear of the first piston ring and the second piston ring can be made substantially uniform, and the durability of the compressor can be improved. Further, if the inner diameter of the passage 11 is increased, the pressure in the lower chamber of the first piston ring can be instantly lowered during the transition from the re-expansion stroke to the suction stroke. The present invention can be applied.

[0021]

According to the present invention, the outer peripheral surface of the piston in the high-pressure side cylinder of the high-pressure side compression section is formed at intervals in the axial direction of the piston and is formed sequentially from the piston head toward the crank chamber side. The first piston ring and the second piston ring are mounted in the concave groove, and one end is within a range in which the lower surface of the first piston ring of the concave groove contacts the lower surface of the first piston ring during the compression stroke. Is opened, and the other end is opened between the piston outer peripheral surface, the first piston ring, the second piston ring and the high pressure side cylinder inner wall in the high pressure side cylinder through a series of passages formed so as to open in the piston. Since the defined space and the crank chamber are made to communicate with each other, the first piston ring and the passage allow the outer peripheral surface of the piston in the high-pressure side cylinder, the first piston ring, and the second piston ring. A space defined between the stone ring and the high pressure side cylinder inner wall and the crank chamber can be communicated with and cut off from each other, and between the piston outer peripheral surface, the first piston ring, the second piston ring and the high pressure side cylinder inner wall. The pressure in the space defined by the second piston ring can be rapidly reduced during the transition from the re-expansion stroke to the suction stroke, the back pressure applied to the second piston ring can be reduced, and the second piston to the inner wall of the high pressure side cylinder can be reduced. The pressing force of the ring can be reduced. Thereby, according to the present invention, the high pressure side cylinder by the first piston ring and the second piston ring,
It is possible to maintain the sealing performance between the pistons and to make the vertical differential pressures of the first piston ring and the second piston ring substantially minimum in each stroke, and to prevent the wear of the first piston ring and the second piston ring. It can be made substantially uniform, and eventually the durability of the multi-stage compressor can be improved. Also, if the inner diameter of the passage is increased, it is defined between the outer peripheral surface of the piston in the high pressure side cylinder, the first piston ring, the second piston ring and the inner wall of the high pressure side cylinder during the transition from the re-expansion stroke to the suction stroke. It is possible to instantly reduce the pressure in the space, so that the present invention can be applied to a multi-stage compressor of any specification.

[Brief description of drawings]

FIG. 1 is a side view of a two-stage compressor showing an embodiment of the present invention.

FIG. 2 is a side sectional view of an essential part showing an embodiment of the present invention.

FIG. 3 is a side cross-sectional view of a main part during a re-expansion stroke showing an embodiment of the present invention.

FIG. 4 is a perspective view of a main part of first and second piston rings according to an embodiment of the present invention.

FIG. 5 is a side cross-sectional view of the essential parts in one state during the transition from the re-expansion stroke to the suction stroke, showing an embodiment of the present invention.

FIG. 6 is a side cross-sectional view of a main part during a suction stroke showing an embodiment of the present invention.

FIG. 7 is a side cross-sectional view of a main part during a compression stroke showing an embodiment of the present invention.

FIG. 8 is a side sectional view of an essential part showing an example of a conventional two-stage compressor.

FIG. 9 is a high-pressure side acupressure diagram of a conventional two-stage compressor.

FIG. 10 is a side cross-sectional view of an essential part of a conventional two-stage compressor during a re-expansion stroke.

FIG. 11 is a side cross-sectional view of an essential part during a suction stroke showing an example of a conventional two-stage compressor.

FIG. 12 is a side sectional view of an essential part of a conventional two-stage compressor during a compression stroke.

[Explanation of symbols]

 1 Cylinder 1a Compression chamber 1b Crank chamber 2 Piston 3 Recessed groove 3a Wall 4 First piston ring 5 Second piston ring

Claims (1)

[Claims] 1. A low-pressure side compression unit and a high-pressure side compression unit,
At least a high-pressure side compression unit, a high-pressure side cylinder, a piston connected to a crankshaft provided in the crank chamber and movably provided inside the high-pressure side cylinder to form a compression chamber in the high-pressure side cylinder, and To form a seal between the compression chamber and the crank chamber of the high-pressure side cylinder, the piston is formed in the high-pressure side cylinder at an outer peripheral surface thereof with a gap in the axial direction of the piston and from the piston head toward the crank chamber side. A multistage compressor comprising a first piston ring and a second piston ring mounted in a recessed groove formed therein, the air pressure being gradually increased from a low-pressure side compression part to a high-pressure side compression part. The first of the recesses of
A series of openings formed on the wall with which the lower surface of the piston ring contacts so that one end opens within the range in which the lower surface of the first piston ring contacts during the compression stroke and the other end opens into the piston in the high-pressure side cylinder. Through the passage of, the space defined between the outer peripheral surface of the piston in the high pressure side cylinder, the first piston ring, the second piston ring and the inner wall of the high pressure side cylinder, and the crank chamber are communicated with each other. Characteristic multi-stage compressor.