ROTARY COMPRESSOR

TECHNICAL FIELD

The present invention relates to a rotary compressor.

BACKGROUND TECHNIQUE

A motor of a compressor is usually controlled by an inverter and a microcomputer. If the number of rotations of the motor is reduced, it is possible to operate, with sufficiently lower ability than rating, a refrigeration cycle apparatus in which the compressor is used. Patent documents 1 and 2 provide one technique for operating the refrigeration cycle apparatus with a low ability using a method which is different from the inverter control.

FIG. 8 is a partially cut-away sectional view showing a configuration of the compressor described in patent document 1. The compressor 601 includes a partition vane 615, a partition vane spring 616, a discharge port 617, a discharge pipe 618 and an opening 619. The partition vane 615 partitions a cylinder 608 into a low pressure chamber and a high pressure chamber. The opening 619 opens at an intermediate portion of the cylinder 608, and is in communication with an opening/closing mechanism 620 provided in the opening 619. The opening/closing mechanism 620 is composed of a plunger 621 and a plunger spring 622. In a state where high pressure gas is not introduced into the plunger 621 from a high pressure-induction pipe 623, the opening 619 and a suction port 612 are connected to each other through a bypass path 624.

A four-way valve 625, a utilization-side heat exchanger 626, a decompressor 627, a heat source-side heat exchanger 628, an accumulator 611 and a suction pipe 629 are connected to the compressor 601 through the discharge pipe 618. The discharge pipe 618, an intermediate portion of the four-way valve 625 and the high pressure-induction pipe 623 are connected to one another through a solenoid valve 630. A piston 607 rotates in a direction of an arrow A.

When the solenoid valve 630 opens, since high pressure gas is introduced into the high pressure-induction pipe 623, the plunger 621 overcomes the plunger spring 622 and closes an opening 610 of the cylinder 608. At this time, most of refrigerant sucked from the suction port 612 into the cylinder 608 is discharged into the discharge pipe 618 through the discharge port 617.

When the solenoid valve 630 closes on the other hand, a pressure difference in the compressor 601 is reduced, the plunger 621 is returned to a position shown in FIG. 8 by a restoring force of the plunger spring 622. Thereafter, if the compressor 601 is operated again, high pressure gas is not introduced into the high pressure-induction pipe 623. The opening 619 formed in an intermediate portion of the cylinder 608 is in communication with the suction port 612 through the bypass path 624. As a result, a portion of refrigerant in the cylinder 608 is returned into the suction port 612 through the bypass path 624 while the refrigerant is being compressed, and refrigerant discharged from the discharge pipe 618 is largely reduced. According to this, it is possible to operate the refrigeration cycle apparatus with lower ability.

FIG. 9 is a vertical sectional view of a compressor described in patent document 2. A first discharge port 714 is formed in a cylinder 710, and a second discharge port 723 is formed in a main bearing 720 such that the second discharge port 723 is in communication with the first discharge port 714 so that compressed gas is discharged into a casing 701. A bypass hole 722 having a bypass valve 780 between the first discharge port 714 and the second discharge port 723 is formed in the main bearing 720.

When the bypass hole 722 closes, most of refrigerant sucked from the suction port 712 into the cylinder 710 is discharged into the casing 701 through the first discharge port 714 and the second discharge port 723.

When high pressure is introduced into the bypass valve 780 and the bypass hole 722 opens on the other hand, since refrigerant sucked from the suction port 712 into the cylinder 710 is returned into the suction port 712 through the first discharge port 714 and the bypass hole 722, refrigerant is not discharged into the casing 701. According to this, it is possible to operate the refrigeration cycle apparatus with lower ability.

PRIOR ART DOCUMENTS
Patent Documents

[Patent Document 1] Japanese Patent Application Laid-open No. S61-93285

[Patent Document 2] Japanese Translation of PCT International Application, Publication No. 2008-509325

SUMMARY OF THE INVENTION
Problem to be Solved by the Invention

One technique for enhancing efficiency of a refrigeration cycle apparatus is to enhance efficiency of a compressor. The efficiency of the compressor largely depends on efficiency of a motor used in the compressor. Many motors exert high efficiency with the number of rotations close to the rated number of rotations (e.g., 60 Hz). Hence, if the motor is driven with low number of rotations (e.g., 30 Hz) using an inverter or the like, it can not be expected to enhance the efficiency of the compressor. When the refrigeration cycle apparatus is operated with ability lower than rated ability (e.g., 30% or less of rated ability), the number of rotations of the rotary compressor is reduced and vibration caused by torque variation is increased, and the rotary compressor cannot be operated with further lower number of rotations (e.g., 20 Hz or less). As a result, the rotary compressor is intermittently operated in such a manner that operation and rest are repeated, and efficiency of the refrigeration cycle apparatus is largely deteriorated.

In patent document 1, when the solenoid valve 630 opens, high pressure gas is introduced into the high pressure-induction pipe 623, and the plunger 621 overcomes the plunger spring 622 and closes the opening 619 of the cylinder 608. However, a volume of the opening 619 becomes dead volume, and this deteriorates the efficiency of the compressor 601.

In patent document 2, since the first discharge port 714 is formed in the cylinder 710, if attempt is made to reduce dead volume of the discharge port, strength of the cylinder 710 is lowered and this causes problems that galling between parts is caused or parts become abnormally worn due to deformation caused by pressure or temperature at the time of operation. If strength of the cylinder 710 is enhanced, dead volume of the discharge port increases, and this deteriorates efficiency of the compressor. To configure a first discharge valve for preventing back-flow of refrigerant from the first discharge port 714 to the compression chamber, it is necessary to secure a certain level of height of the cylinder 710. Especially when high density refrigerant such as R410 and carbon dioxide is used as refrigerant as working fluid, a load of a shaft or a vane is increased, a machine loss increases, a leakage loss while refrigerant is compressed increases and the efficiency of the compressor is deteriorated.

In view of such circumstances, it is an object of the present invention to provide a rotary compressor capable of exerting high efficiency from high ability to low ability of a refrigeration cycle apparatus.

Means for Solving the Problem

That is, the present invention provides a rotary compressor in which a compression mechanism includes: a cylinder; a piston disposed in the cylinder; a frame which rotatably holds a shaft, which covers both upper and lower sides of the cylinder, and which forms an operation chamber between the frame and an inner peripheral surface of the cylinder; and a vane which partitions the operation chamber into a suction chamber and a compression-discharge chamber, and in which a motor operates the piston through the shaft, wherein the rotary compressor includes: a hermetic container in which the compression mechanism and the motor are accommodated; a suction path for guiding working fluid to be compressed to the suction chamber; a discharge port which is provided in the frame, and through which compressed working fluid flows out from the operation chamber; an interior space which is partitioned from an interior of the hermetic container and the operation chamber; a communication passage between the interior space and the suction path; a first passage between the discharge port and the interior space; a first check valve which prohibits working fluid passing through the first passage from returning from the interior space to the discharge port; a second passage between the interior space and the interior of the hermetic container; a second check valve which prohibits working fluid passing through the second passage from returning from the interior of the hermetic container to the interior space; and a control mechanism which is provided in the communication passage and which controls pressure in the interior space.

Effect of the Invention

According to the present invention, by making working fluid return from the operation chamber to the suction path using the communication passage, it is possible to operate the rotary compressor with relatively small suction volume. If working fluid is prohibited to return from the operation chamber to the suction path on the other hand, it is possible to operate the rotary compressor with relatively large suction volume, i.e., with normal suction volume. When the control mechanism and the inverter are controlled such that reduction of the suction volume is compensated by increase in the number of rotations of the motor, the suction volume is reduced instead of driving the motor with the low number of rotations. Therefore, it is possible to provide a rotary compressor capable of exerting high efficiency from high ability to low ability of a refrigeration cycle apparatus.

Further, according to the present invention, since there is no opening which opens toward the cylinder, it is possible to prevent the efficiency of the compressor from being deteriorated by dead volume. It is possible to secure the strength of the cylinder, and to prevent galling between parts and abnormal wearing of parts which may be caused due to deformation caused by pressure or temperature at the time of operation. Further, since it is possible to lower the height of the cylinder, if high density refrigerant such as R410A, carbon dioxide, R32, R407C, HFO-1234yf and R134a is used as refrigerant as the working fluid, since it is possible to prevent a machine loss from increasing by increase in a load of a shaft or a vane, and to prevent a leakage loss from increasing while refrigerant is compressed and therefore, it is possible to provide a rotary compressor capable of exerting high efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of a rotary compressor according to a first embodiment;

FIG. 2 is a vertical sectional view of a rotary compressor according to a second embodiment;

FIG. 3A is a control flowchart of a control unit (on-off valve) and an inverter;

FIG. 3B is another control flowchart of the control unit (on-off valve) and the inverter;

FIG. 4 is a graph showing a relation between ability of a rotary compressor, suction volume of a compression mechanism, a state of an on-off valve and the number of rotations of a motor;

FIG. 5 is a graph showing a relation between ability of the rotary compressor and efficiency of the rotary compressor;

FIG. 6 is a vertical sectional view of a rotary compressor according to a third embodiment;

FIG. 7 is a block diagram of a refrigeration cycle apparatus using the rotary compressor of the third embodiment;

FIG. 8 is a partial sectional view showing a configuration of a conventional compressor; and

FIG. 9 is a vertical sectional view of another conventional compressor.

EXPLANATION OF SYMBOLS

1 hermetic container

2 motor

3 compression mechanism

4 shaft

5 cylinder

6 upper frame

7 lower frame

8 piston

9 vane

12 accumulator

14 suction path

16 communication passage

22 oil reservoir

25 operation chamber

28 interior space

29 discharge port

30 control mechanism

32 on-off valve

34
a first passage

34
b second passage

35
a first check valve

35
b second check valve

40 compressor body

42 inverter

44 control unit

90 three-way valve

92 high pressure path

100, 200, 300 rotary compressor

MODE FOR CARRYING OUT THE INVENTION
First Embodiment

As shown in FIG. 1, a rotary compressor 100 of a first embodiment includes a compressor body 40, an accumulator 12, a discharge path 11, a suction path 14, a communication passage 16, a control mechanism 30, an inverter 42 and a control unit 44.

The compressor body 40 includes a hermetic container 1, a motor 2, a compression mechanism 3 and a shaft 4. The compression mechanism 3 is disposed at a lower location in the hermetic container 1. In the hermetic container 1, the motor is disposed above the compression mechanism 3. The compression mechanism 3 and the motor 2 are connected to each other through the shaft 4. An upper portion of the hermetic container 1 is provided with a terminal 21 for supplying electricity to the motor 2. An oil reservoir 22 in which lubricant oil is held is formed in a bottom of the hermetic container 1. The compressor body 40 has a so-called hermetic compressor structure.

The discharge path 11, the suction path 14 and the communication passage 16 are respectively composed of refrigerant pipes.

The discharge path 11 penetrates an upper portion of the hermetic container 1, and opens in the hermetic container 1. The discharge path 11 guides compressed working fluid (typically, refrigerant) to outside of the compressor body 40. The suction path 14 has one end connected to the compression mechanism 3 and the other end connected to the accumulator 12.

The suction path 14 penetrates a barrel of the hermetic container 1.

The suction path 14 guides refrigerant to be compressed from the accumulator 12 to an operation chamber 25 of the compression mechanism 3. The communication passage 16 has one end connected to the compression mechanism 3 at a position different from that of the suction path 14, and the other end connected to the accumulator 12. The communication passage 16 penetrates the barrel of the hermetic container 1.

The communication passage 16 returns refrigerant which is once sucked into the operation chamber 25 of the compression mechanism 3 to the suction path 14 before the refrigerant is compressed.

The compression mechanism 3 is a positive displacement type fluid mechanism. The compression mechanism 3 is driven by the motor 2 and compresses refrigerant. As shown in FIG. 1, the compression mechanism 3 is composed of a cylinder 5, a piston 8, a vane 9, a spring 10, an upper frame 6 and a lower frame 7. The piston 8 fitted over an eccentric portion 4a of the shaft 4 is disposed in the cylinder 5. The operation chamber 25 is formed between an outer peripheral surface of the piston 8 and an inner peripheral surface of the cylinder 5. A vane groove (not shown) is formed in the cylinder 5. The vane 9 has a tip end which comes into contact with the outer peripheral surface of the piston 8, and the vane 9 is accommodated in the vane groove. The spring 10 is disposed in the vane groove. The vane 9 is pushed toward the piston 8.

The upper frame 6 and the lower frame 7 are respectively provided on an upper side and a lower side of the cylinder 5 such that the upper frame 6 and the lower frame 7 sandwich the cylinder 5 to cover the same. The operation chamber 25 between the cylinder 5 and the piston 8 is partitioned by the vane 9. According to this, the operation chamber 25 (suction chamber) and the operation chamber 25 (compression-discharge chamber) are formed. Refrigerant to be compressed is guided to the operation chamber 25 (suction chamber) through the suction path 14. Compressed refrigerant flows out from the operation chamber 25 (compression-discharge chamber) and from a discharge port 29 formed in the upper frame 6. The interior space 28 which is partitioned from an interior of the hermetic container 1 and the operation chamber 25 is provided in the upper frame 6 on the opposite side from the operation chamber 25, a first passage 34a is formed between the discharge port 29 and the interior space 28, and the interior space 28 and the discharge port 29 are in communication with each other. The first passage 34a is provided with a first check valve 35a to prevent refrigerant from flowing from the interior space 28 to the operation chamber 25. A second passage 34b is formed between the interior space 28 and the interior of the hermetic container 1, and the interior space 28 and the interior of the hermetic container 1 are in communication with each other. The second passage 34b is provided with a second check valve 35b to prevent refrigerant from flowing from the interior of the hermetic container 1 to the interior space 28.

The vane 9 may be integral with the piston 8. That is, the piston 8 and the vane 9 may be composed of a swing piston, or the vane 9 and the piston 8 may be joined to each other.

The motor 2 is composed of a stator 17 and a rotor 18. The stator 17 is fixed to an inner peripheral surface of the hermetic container 1. The rotor 18 is fixed to the shaft 4 and rotates together with the shaft 4. The piston 8 is moved in the cylinder 5 by the motor 2. As the motor 2, it is possible to use a motor whose number of rotations can be changed. Examples of such a motor are an IPMSM (Interior Permanent Magnet Synchronous Motor) and an SPMSM (Surface Permanent Magnet Synchronous Motor).

The control unit 44 controls the inverter 42 and adjusts the number of rotations of the motor 2, i.e., the number of rotations of the rotary compressor 100. As the control unit 44, it is possible to use a DSP (Digital Signal Processor) including an A/D conversion circuit, an input/output circuit, a computation circuit and a storage unit.

The accumulator 12 is composed of an accumulation container 12a and an introduction pipe 12b. The accumulation container 12a includes an interior space capable of holding liquid refrigerant and gas refrigerant. The introduction pipe 12b penetrates an upper portion of the accumulation container 12a, and opens toward the interior space of the accumulation container 12a. The other end of the suction path 14 and the other end of the communication passage 16 are connected to the accumulator 12. The other end of the suction path 14 and the other end of the communication passage 16 penetrate a bottom of the accumulation container 12a, upwardly extend from the bottom of the accumulation container 12a, and open in the interior space of the accumulation container 12a at given heights. That is, the communication passage 16 is connected to the suction path 14 through the interior space of the accumulator 12. To reliably prevent liquid refrigerant from directly flowing from the introduction pipe 12b to the suction path 14, other member such as a baffle may be provided in the accumulation container 12a. The communication passage 16 may be connected directly to the suction path 14 or the introduction pipe 12b.

The control mechanism 30 is provided in the communication passage 16 at a location outside of the compressor body 40. In this embodiment, the control mechanism 30 is composed of an on-off valve 32. One end of the communication passage 16 which is connected to the compression mechanism 3 is in communication with the interior space 28. The control mechanism 30 changes a suction volume of the rotary compressor 100.

When the on-off valve 32 is opened, as a volume of the operation chamber 25 reduces, the first check valve 35a opens and refrigerant is discharged to outside of the operation chamber 25. The discharged refrigerant is returned to the suction path 14 through the communication passage 16. Hence, pressure in the operation chamber 25 does not rise. At this time, since refrigerant is not discharged from the interior space 28 into the hermetic container 1, the rotary compressor 100 is operated in a state where its suction volume is substantially zero.

When the on-off valve 32 is closed, refrigerant can not return from the operation chamber 25 to the suction path 14 through the communication passage 16. Hence, if a suction stroke is completed, a compression stroke starts immediately. At this time, since the first check valve 35a prevents refrigerant from reversely flowing from the interior space 28 to the operation chamber 25, pressure in the interior space 28 rises. Further, when pressure in the interior space 28 rises and becomes higher than pressure in the hermetic container 1, the second check valve 35b opens and refrigerant is discharged into the hermetic container 1. At this time, the rotary compressor 100 is operated with a normal suction volume.

The rotary compressor 100 of this embodiment controls the inverter 42 and adjusts the number of rotations of the motor 2, i.e., the number of rotations of the rotary compressor 100. However, when the refrigeration cycle apparatus is operated with ability lower than the rated ability (e.g., 30% or less of the rated ability), the number of rotations of the rotary compressor 100 is reduced, this reduction increases the vibration caused by torque variation, and the rotary compressor 100 can not be operated with further lower number of rotations (e.g., 20 HZ or less). As a result, the rotary compressor 100 is intermittently operation in such a manner that operation and rest are repeated, and efficiency of the refrigeration cycle apparatus is largely deteriorated.

Hence, a so-called “ability variable technique based on switching of a suction volume” is widely known. In this technique, a portion of refrigerant which is compressed by the cylinder 5 is made to bypass to outside of the cylinder 5, thereby changing a suction volume of the operation chamber 25. As a switching operation of the suction volume, the rotary compressor 100 of this embodiment can realize a so-called digital compressor technique in which a case where the rotary compressor 100 is operated with substantially zero suction volume by opening the on-off valve 32 and a case where the rotary compressor 100 is operated with a normal suction volume by closing the on-off valve 32 are combined to control the ability.

In the rotary compressor 100 of this embodiment, the on-off valve 32 is opened and closed. For example, by opening the on-off valve 32 for five seconds and closing the on-off valve 32 for five seconds, the ability of operation for total ten seconds can be made 50%. As a result, even when the refrigeration cycle apparatus is operated with ability lower than the rated ability, since the rotary compressor 100 can continuously be operated, the refrigeration cycle apparatus can be operated efficiently.

When the rotary compressor 100 of this embodiment is operated with a normal suction volume by closing the on-off valve 32, since there is no opening facing the cylinder 5, it is possible to prevent the efficiency of the compressor from being deteriorated by dead volume. That is, in the normal rotary compressor 100, the operation chamber 25 between the cylinder 5 and the piston 8 is partitioned by the vane 9 and according to this, the operation chamber 25 (suction chamber) and the operation chamber 25 (compression-discharge chamber) are formed. Refrigerant to be compressed is guided to the operation chamber 25 (suction chamber) through the suction path 14. Here, if the opening exists in the cylinder 5, refrigerant in the operation chamber 25 is held in the opening when the opening is in communication with the operation chamber 25 (compression-discharge chamber), but if the opening is brought into communication with the operation chamber 25 (suction chamber), since pressure of refrigerant in the opening is higher than pressure of refrigerant in the operation chamber 25 (suction chamber), refrigerant in the opening reversely flows toward the operation chamber 25 (suction chamber). At this time, the refrigerant in the operation chamber 25 (suction chamber) is reduced and volume efficiency is deteriorated. Since the refrigerant in the opening is not discharged into the hermetic container 1, compression power is lost correspondingly and input of the compressor is increased. This series of loss is called efficiency reduction of a compressor caused by dead volume.

When the rotary compressor 100 of this embodiment is operated with a normal suction volume by closing the on-off valve 32, the discharge port 29 through which compressed working fluid flows out from the operation chamber 25 is formed in the upper frame 6. According to this configuration, since it is possible to secure the strength of the cylinders, it is possible to avoid a case where galling between parts is caused or parts become abnormally worn due to deformation caused by pressure or temperature at the time of operation. Further, a height of the cylinder 5 is not limited by a configuration of the check valve. As a result, when high density refrigerant such as R410A and carbon dioxide is used as working fluid, since the height of the cylinder 5 can be lowered, it is possible to reduce the increase in a machine loss caused by increase in a load of the shaft 4 or the vane 9 and to reduce a gap formed between an inner periphery of the cylinder 5 and an outer periphery of the piston 8, it is possible to prevent a leakage loss caused when refrigerant is being compressed from increasing. As a result, it is possible to provide the rotary compressor 100 capable of exerting high efficiency.

When the rotary compressor 100 of this embodiment is operated with a normal suction volume by closing the on-off valve 32, the first check valve 35a and the second check valve 35b are configured in an end surface direction. According to this configuration, since refrigerant which flows out from the discharge port 29 can smoothly flow into the interior space 29 and the hermetic container 1, it is possible to provide a rotary compressor 100 capable of suppressing a loss caused when refrigerant is discharged from the operation chamber 25 and capable of exerting high efficiency.

The rotary compressor 100 of this embodiment is configured such that when it is operated with the normal suction volume by closing the on-off valve 32, a cross-sectional area of the second passage 34b becomes greater than that of the first passage 34a. According to this configuration, since the first passage 34a opens at the cylinder 5, if the cross-sectional area of the first passage 34a is increased, efficiency of the compressor is deteriorated by the dead volume. If the cross-sectional area of the first passage 34a is reduced on the other hand, pressure in the operation chamber 25 rises higher than discharge pressure by resistance of refrigerant which flows out from the operation chamber 25 through the discharge port 29, and compression power is increased. Hence, it is necessary that the cross-sectional area of the first passage 34a is determined such that the efficiency of the rotary compressor 100 becomes the highest. However, since the second passage 34b is provided between the interior space 29 and the interior of the hermetic container 1, the efficiency of the compressor is not deteriorated by the dead volume. That is, by suppressing pressure rise in the interior space 29 by the resistance of refrigerant which flows out through the second passage 34b, performance of the rotary compressor 100 is enhanced. As a result, by setting the cross-sectional area of the second passage 34b greater than that of the first passage 34a, it is possible to provide the rotary compressor 100 capable of exerting high efficiency.

The first check valve 35a and the second check valve 35b can be composed of reed valves which are composed of reed portions 36a and 36b and valve stoppers 37a and 37b, respectively. As a check valve of another type, there is a free valve (not shown) composed of a valve body, a guide and a spring. As a check valve of another type, the check valve can be composed of a plunger and a plunger spring (not shown). If the plunger and the plunger spring are used, since the check valve can always be opened, it is possible to reduce a pressure loss generated in the check valve. Here, the free valve is characterized in that a pressure loss when working fluid passes therethrough can be made smaller than that of a reed valve. However, in the rotary compressor 100 of this embodiment, if the on-off valve 32 is closed from its opened state, there is a problem that pressure in the interior space 29 rises and the valve body collides against the guide and noise is generated until the valve body closes the passage. Hence, it is preferable that the reed valve is used in the rotary compressor 100 of this embodiment.

Next, a relation between an ability variable technique carried out by switching the suction volume and the inverter 42 which drives the motor 2 with an arbitrary number of rotations will be described.

First, a case where the refrigeration cycle apparatus is operated with 70% ability.

A so-called “ability variable technique based on switching of a suction volume” is used. In this technique, a portion of refrigerant which is compressed by the cylinder 5 is made to bypass to outside of the cylinder 5, thereby changing a suction volume of the operation chamber 25. In this case, in the rotary compressor 100 of this embodiment, the on-off valve 32 is opened and closed. For example, by opening the on-off valve 32 for three seconds and closing the on-off valve 32 for seven seconds, the ability of operation for total ten seconds can be made 70%.

By repeating the opening and closing operations of the on-off valve 32 and by changing the ratio between the opening time and closing time in the opening and closing operations, it is possible to change the ability of the refrigeration cycle apparatus. That is, when the opening and closing operations of the on-off valve 32 are repeated, if the ratio of the opening time is increased, the ability of the refrigeration cycle apparatus can be reduced.

When the ability is controlled using the ability variable technique based on switching of the suction volume as described above, it is necessary that the time during which the rotary compressor 100 is operated with substantially zero suction volume is set to 30% by opening the on-off valve 32. At this time, since the rotary compressor 100 keeps rotating, a machine loss is generated to drive the compression mechanism 3 even if power for compressing refrigerant becomes zero.

When the motor 2 is driven by the inverter 42 with an arbitrary number of rotations on the other hand, if the motor 2 is operated with 70% number of rotations (e.g., 42 Hz) of the rated number of rotations (e.g., 60 Hz), the ability can be made 70%. Many motors 2 are designed such that the highest efficiency is exerted with the number of rotations close to the rated number of rotations (e.g., 60 Hz), but if the motor 2 is operated with about 70% number of rotations (e.g., 42 Hz), high efficiency can be maintained. As a result, if an inverter 42 which drives the motor 2 with an arbitrary number of rotations is used, it is possible to operate the refrigeration cycle apparatus efficiently.

Next, a case where the refrigeration cycle apparatus is operated with 50% ability will be described.

When the so-called “ability variable technique based on switching of a suction volume” is used, the on-off valve 32 is opened and closed in the rotary compressor 100 of this embodiment. For example, by opening the on-off valve 32 for five seconds and closing the on-off valve 32 for five seconds, the ability of operation for total ten seconds can be made 50%.

When the motor 2 is driven by the inverter 42 with an arbitrary number of rotations on the other hand, if the motor 2 is operated with 50% number of rotations (e.g., 30 Hz) of the rated number of rotations (e.g., 60 Hz), the ability can be made 50%. However, many motors 2 are designed such that the highest efficiency is exerted with the number of rotations close to the rated number of rotations (e.g., 60 Hz), if the motor 2 is operated with about 50% number of rotations (e.g., 30 Hz), the efficiency is largely deteriorated. As a result, if the ability variable technique based on the switching of the suction volume is used, it is possible to operate the refrigeration cycle apparatus efficiently.

Hence, concerning a relation between the ability variable technique based on the switching of the suction volume and the inverter 42 which drives the motor 2 with an arbitrary number of rotations, if an inverter 42 which can operate the refrigeration cycle apparatus efficiently is selected, it is possible to operate the refrigeration cycle apparatus more efficiently.

In this embodiment, the ability variable technique based on the switching of the suction volume and the inverter 42 which drives the motor 2 with an arbitrary number of rotations are appropriately separately used depending upon situations. The ability variable technique based on the switching of the suction volume is selected when the refrigeration cycle apparatus is operated with 70% ability, the inverter 42 which drives the motor 2 with an arbitrary number of rotations is selected when the refrigeration cycle apparatus is operated with 50% ability, but the invention is not limited to this embodiment. Concerning a question as to which one of the ability variable technique and the inverter should used for controlling the ability of the refrigeration cycle, it is preferable to select one of them which can operate the refrigeration cycle apparatus more efficiently.

Second Embodiment

As shown in FIG. 2, a rotary compressor 200 of a second embodiment includes a second compression mechanism 33 in addition to the compression mechanism 3 described in the first embodiment. In the following description, “first” is added to the elements of the compression mechanism 3 described in the first embodiment. For example, the cylinder 5 is described as a first cylinder 5, the piston 8 is described as a first piston 8, the vane 9 is described as a first vane 9, the operation chamber 25 is described as a first operation chamber 25, and the compression mechanism 3 is described as a first compression mechanism 3.

The second compression mechanism 33 is composed of a second cylinder 55, a second piston 58, a second vane 59 and a second spring 60. The second cylinder 55 is disposed concentrically with the first cylinder 5. A second piston 58 fitted over a second eccentric portion 4b of a shaft 4 is disposed in the second cylinder 55. A second operation chamber 75 is formed between an outer peripheral surface of the second piston 58 and an inner peripheral surface of the second cylinder 55. A second vane groove (not shown) is formed in the second cylinder 55. A second vane 59 is accommodated in the second vane groove. A tip end of the second vane 59 is in contact with the outer peripheral surface of the second piston 58. A second spring 60 is disposed in the second vane groove. The second spring 60 pushes the second vane 59 toward the second piston 58. A second operation chamber 75 between the second cylinder 55 and the second piston 58 is partitioned by the second vane 59. According to this, a second operation chamber 75 (second suction chamber) and a second operation chamber 75 (second compression-discharge chamber) are formed. Refrigerant to be compressed is guided to the second operation chamber 75 (second suction chamber) through a second suction path 15. A second discharge port 79 is formed in an upper frame 6. According to this, compressed refrigerant is guided from the second operation chamber 75 (second compression-discharge chamber) into the hermetic container 1 through the second discharge port 79. A discharge valve 35c is provided in the second discharge port 79. According to this, refrigerant does not reversely flow from the hermetic container 1 into the second operation chamber 75.

In the first compression mechanism 3, refrigerant to be compressed is guided to the first operation chamber 25 (suction chamber) through the first suction path 14. Compressed refrigerant flows out from a first discharge port 29 which is formed from the first operation chamber 25 (compression-discharge chamber) to the lower frame 7. The interior space 28 which is partitioned from an interior of the hermetic container 1, the first operation chamber 25 and the second operation chamber 75 is provided in the upper frame 7 on the opposite side from the operation chamber 25, a first passage 34a is formed between the discharge port 29 and the interior space 28, and the interior space 28 and the discharge port 29 are in communication with each other. The first passage 34a is provided with a first check valve 35a to prevent refrigerant from flowing from the interior space 28 to the first operation chamber 25. A second passage 34b is formed between the interior space 28 and the interior of the hermetic container 1, and the interior space 28 and the interior of the hermetic container 1 are in communication with each other. The second passage 34b is provided with a second check valve 35b to prevent refrigerant from flowing from the interior of the hermetic container 1 to the interior space 28.

It is preferable that the first operation chamber 25 is located in the vertically downward direction with respect to the second operation chamber 75. This is because when the refrigeration cycle apparatus operated with low ability, since only suction refrigerant passes through the first operation chamber 25, temperature of the cylinder becomes low. Further, this is because if the low temperature cylinder is located at a low location, it is possible to restrain the suction refrigerant from receiving heat from discharged refrigerant from a standpoint of temperature stratification.

The lower frame 7 is covered with a muffler 23. The muffler 23 has a space capable of receiving refrigerant which is compressed by the first compression mechanism 3. A flow path 26 penetrates the lower frame 7, the first cylinder 5, a middle plate 53, the second cylinder 55 and the upper frame 6. According to this configuration, refrigerant moves from the space of the muffler 23 into the hermetic container 1.

A projecting direction of the first eccentric portion 4a is deviated from a projecting direction of the second eccentric portion 4b by 180°. That is, a phase of the first piston 8 is deviated from a phase of the second piston 58 by a rotation angle of the shaft of 180°.

Refrigerant is supplied to the first compression mechanism 3 through the first suction path 14. Refrigerant is supplied to the second compression mechanism 33 through the second suction path 15. Refrigerant is compressed by the first compression mechanism 3 or the second compression mechanism 33 and discharged into the hermetic container 1. The first suction path 14 and the second suction path 15 are connected to the accumulator 12. One of the suction paths 14 and 15 may branch off from the other one inside or outside of the accumulator 12.

As shown in FIG. 2, since the communication passage 16 is not connected to the second compression mechanism 33, a suction volume of the second compression mechanism 33 is always constant. The communication passage 16 is connected only to the first compression mechanism 3 so that only a suction volume of the first compression mechanism 3 can be changed. According to this, production costs of the rotary compressor 200 can be suppressed. Of course, the communication passage 16 may be connected to the first compression mechanism 3 and the second compression mechanism 33 so that suction volumes of the first compression mechanism 3 and the second compression mechanism 33 can be changed.

In this embodiment, the first compression mechanism 3 is disposed on a side far from the motor 2 and the second compression mechanism 33 is disposed on a side close to the motor 2. That is, the motor 2, the second compression mechanism 33 and the first compression mechanism 3 are arranged in this order along an axial direction of the shaft 4. Since the second compression mechanism 33 has the constant suction volume, the second compression mechanism 33 requires greater torque than that of the first compression mechanism 3 which can be operated with substantially zero suction volume. Therefore, since the second compression mechanism 33 is disposed on the side close to the motor 2, a load which is applied to the shaft 4 when the first compression mechanism 3 is operated with the substantially zero suction volume is reduced. According to this, it is possible to reduce machine losses of the upper frame 6 and the lower frame 7. If the first compression mechanism 3 which can be operated with the substantially zero suction volume is disposed on a lower side, it is possible to reduce a pressure loss which is generated when compressed refrigerant flows into the interior space 28 of the hermetic container 1 through the muffler 23. However, a positional relation between the first compression mechanism 3 and the second compression mechanism 33 is not limited to the above-described relation.

In this embodiment, a normal suction volume of the first compression mechanism 3 and a suction volume of the second compression mechanism 33 are the same. Here, a case where the first compression mechanism 3 is operated with substantially zero suction volume is defined as a low volume mode, and a case where the first compression mechanism 3 is operated with a normal suction volume is defined as a high volume mode. At this time, if a suction volume in the high volume mode of the rotary compressor 200 is defined as V, a suction volume in the low volume mode is V/2.

Next, the inverter 42 which drives the motor 2 with an arbitrary number of rotations, and control procedure of the control mechanism 30 (on-off valve 32) and the inverter 42 performed by the control unit 44 which controls the inverter 42 will be described with reference to FIG. 3A.

In step 1, the number of rotations of the motor 2 is adjusted in accordance with requested ability. More specifically, the number of rotations of the motor 2 is adjusted so that a necessary flow rate of refrigerant is obtained. In steps 2 and 6, it is determined whether the number of rotations of the motor 2 is reduced or increased. If it is determined in step 2 that the number of rotations is reduced, the procedure proceeds on to step 3, and it is determined whether the current number of rotations is 30 Hz or less. If the current number of rotations is 30 Hz or less, it is determined in step 4 whether the on-off valve 32 is closed. If the on-off valve 32 is closed, processing to open the on-off valve 32 and processing to increase the number of rotations of the motor 2 to a double value of the current number of rotations are carried out. Although the order of the processing operations in step 5 is not especially limited, it is possible to increase the number of rotations of the motor 2 substantially at the same time when the on-off valve 32 is opened.

If it is determined in step 2 that processing to increase the number of rotations is carried out on the other hand, the processing proceeds on to step 7, and it is determined whether the current number of rotations is 70 Hz or more. If the current number of rotations is 70 Hz or more, it is determined in step 8 whether the on-off valve 32 is opened. If the on-off valve 32 is opened, processing to close the on-off valve 32 and processing to reduce the number of rotations of the motor 2 to ½ of the current number of rotations are carried out in step 9. Although the order of the processing operations in step 9 is not especially limited, it is possible to reduce the number of rotations of the motor 2 substantially at the same time when the on-off valve 32 is closed.

By carry out the control in accordance with the flowchart in FIG. 3A, a relation between a state of the on-off valve 32 and the number of rotations of the motor 2 has hysteresis as shown in FIG. 4. According to such control, it is possible to prevent hunting of the compression mechanism 3.

According to the rotary compressor 200 of this embodiment, in a state where the on-off valve 32 is closed, i.e., in the high volume mode in which refrigerant is prohibited from returning from the operation chamber 25 to the suction path 14 through the communication passage 16, a suction volume of the compression mechanism 3 is “V”. When the number of rotations of the motor 2 is reduced from the high rotation side to the first number of rotations (e.g., 30 Hz) or less during operation in the high volume mode, the control unit 44 carries out processing concerning the on-off valve 32 to reduce the suction volume and processing concerning the inverter 42 to increase the number of rotations of the motor 2. The processing concerning the on-off valve 32 to reduce the suction volume is processing to open the on-off valve 32. The processing concerning the inverter 42 to increase the number of rotations of the motor 2 is processing to set the target number of rotations of the motor 2 to a double value of the last number of rotations.

The control unit 44 controls the on-off valve 32 and the inverter 42 to compensate for the increase in the suction volume by reducing the number of rotations of the motor 2. A state where the on-off valve 32 is opened, i.e., in the low volume mode in which refrigerant is prohibited from returning from the operation chamber 25 to the suction path 14 through the communication passage 16, a suction volume of the compression mechanism 3 is “V/2”. When the number of rotations of the motor 2 is increased to the second number of rotations (e.g., 70 Hz) or more during operation in the low volume mode, the control unit 44 carries out processing concerning the on-off valve 32 to increase the suction volume and processing concerning the inverter 42 to reduce the number of rotations of the motor 2. The processing concerning the on-off valve 32 to increase the suction volume is processing to close the on-off valve 32. The processing concerning the inverter 42 to reduce the number of rotations of the motor 2 is processing to set the target number of rotations of the motor 2 to ½ of the last number of rotations.

As shown in FIG. 4, if the number of rotations of the motor 2 is reduced to 30 Hz in a state where the on-off valve 32 is closed, the on-off valve 32 is opened and the number of rotations of the motor 2 is increased to 60 Hz. If the number of rotations of the motor 2 is increased to 70 Hz in a state where the on-off valve 32 is opened, the on-off valve 32 is closed and the number of rotations of the motor 2 is reduced to 35 Hz. If the number of rotations when the on-off valve 32 is opened and the number of rotations of the motor 2 is increased is defined as the third number of rotations and the number of rotations when the on-off valve 32 is closed and the number of rotations of the motor 2 is reduced is defined as the fourth number of rotations, a relation (first number of rotations)<(fourth number of rotations) and a relation (third number of rotations)<(second number of rotations) are established. For example, if the first number of rotations is set to 30 Hz or less, it is possible to operate the rotary compressor 200 with wider ability. A lower limit value of the first number of rotations is not especially limited, but an example of the lower limit value is 20 Hz.

When the control mechanism 30 is controlled such that the first compression mechanism 3 is operated with substantially zero suction volume, the inverter 42 is controlled to compensate for reduction of the suction volume by increasing the number of rotations of the motor 2. According to this, it becomes unnecessary to largely reduce the number of rotations of the motor 2 even when the refrigeration cycle apparatus is operated with ability lower than the rated ability. That is, even when the refrigeration cycle apparatus is operated with low ability, it is possible to drive the motor 2 with the number of rotations capable of exerting high efficiency. Therefore, efficiency of the rotary compressor 200 is also enhanced.

More specifically, as shown by solid lines in FIG. 5, the rotary compressor 200 in this embodiment can exert high efficiency even when the rotary compressor 200 is operated with low ability. In FIG. 5, the rated ability of the rotary compressor 200 is defined as “100%”. If the rated ability is a criterion, the efficiency of the rotary compressor 200 is lowered as the ability to be exerted is lowered, i.e., as the number of rotations of the motor 2 is reduced. As shown by broken lines, when the motor 2 is driven with the number of rotations which is 50% or less of the rated number of rotations, the efficiency is largely deteriorated. In this embodiment, when relatively low ability is required, the motor 2 is operated in the low volume mode having a suction volume V/2. According to this, it is possible to drive the motor 2 with the number of rotations which is close to the rated number of rotations as close as possible. Therefore, even in a region where necessary ability is 50% or less of the rated ability, it is possible to provide a rotary compressor 200 capable of exerting high efficiency.

It is not absolutely necessary to completely 100% compensate for reduction in ability of the rotary compressor 200 caused by reduction of a suction volume by increasing ability of the rotary compressor 200 by increasing the number of rotations of the motor 2. For example, when the on-off valve 32 is opened and a suction volume is reduced to ½, if the number of rotations of the motor 2 is increased by two times, ability of the rotary compressor 200 is not changed by the switching operation between the modes. However, even if ability of the rotary compressor 200 is increased or reduced by the switching operation between the modes, there is no problem.

Heights of the first cylinder 5 and the second cylinder 55 may be made different from each other in accordance with a rate of suction volumes to be changed, and a normal suction volume of the first compression mechanism 3 and a suction volume of the second compression mechanism 33 may be changed. More specifically, when a suction volume of the first compression mechanism 3 is defined as V1 and a suction volume of the second compression mechanism 33 is defined as V2, a suction volume VH in the high volume mode is V1+V2, and a suction volume VL in the low volume mode is V2. Usually, it is preferable that a ratio (VL/VH) of the suction volume VL in the low volume mode to the suction volume VH in the high volume mode is in a range of 0.2 to 0.8.

If the heights of the first cylinder 5 and the second cylinder 55 are made different from each other in accordance with a rate of suction volumes to be changed and the normal suction volume of the first compression mechanism 3 and the suction volume of the second compression mechanism 33 are changed, more specifically, if the suction volume of the first compression mechanism 3 is defined as V1 and the suction volume of the second compression mechanism 33 is defined as V2, the suction volume in the high volume mode is V1+V2, and the suction volume in the low volume mode is V2. This situation will be discussed below. At this time, if the high volume mode and the low volume mode are switched, the number of rotations of the motor 2 can be adjusted in accordance with the ratio (VL/VH) of the suction volume VL in the low volume mode to the suction volume VH in the high volume mode. When the high volume mode is switched to the low volume mode, the number of rotations (target number of rotations) of the motor 2 is set to the number of rotations which is obtained by dividing the number of rotations of the motor 2 immediately before the switching operation between the modes by the ratio (VL/VH). Similarly, when the low volume mode is switched to the high volume mode, the number of rotations of the motor 2 is set to the number of rotations which is obtained by multiplying the number of rotations of the motor 2 immediately before the switching operation between the modes by the ratio (VL/VH). According to this, it is possible to smoothly switch between the operation modes of the high volume mode and the low volume mode.

This embodiment does not have ability in which the control mechanism 30 decompresses refrigerant. Sucked refrigerant is not substantially compressed in the compression-discharge chamber and returned into the first suction path 14 through the communication passage 16. Therefore, deterioration in efficiency caused by a pressure loss is extremely small. However, the embodiment may have the ability in which the control mechanism 30 decompresses refrigerant only within a range not largely affecting the efficiency of the rotary compressor 200.

Next, another control procedure of the on-off valve 32 and the inverter 42 will be described.

Even when the number of rotations of the motor 2 is reduced to the first number of rotations (e.g., 30 Hz) in the high volume mode, if a flow rate of refrigerant is excessively large, the control unit 44 may carry out the processing concerning the on-off valve 32 to reduce the suction volume and the processing concerning the inverter 42 to increase the number of rotations of the motor 2. That is, the control unit 44 determines whether it is necessary to switch between the modes before the number of rotations of the motor 2 is actually reduced to the first number of rotations. Similarly, even when the number of rotations of the motor 2 is increased to the second number of rotations (e.g., 70 Hz) in the low volume mode, if the flow rate of refrigerant is not sufficient, the control unit 44 may carry out the processing concerning the on-off valve 32 to increase the suction volume and the processing concerning the inverter 42 to reduce the number of rotations of the motor 2. That is, the control unit 44 determines whether it is necessary to switch between the modes before the number of rotations of the motor 2 is actually increased to the second number of rotations. An example of such control will be described with reference to FIG. 3B.

As shown in FIG. 3B, the necessary number of rotations of the motor 2 is first calculated in step 11. Here, “necessary number of rotations” means the number of rotations for obtaining a necessary flow rate of refrigerant. Next, it is determined in step 12 whether the necessary number of rotations is equal to or less than the first number of rotations (e.g., 30 Hz). If the necessary number of rotations is equal to or less than the first number of rotations, it is determined in step 13 whether the on-off valve 32 is closed. If the on-off valve 32 is closed, in step 15, the on-off valve 32 is opened and the number of rotations of the motor 2 is adjusted to a value capable of obtaining a necessary flow rate of refrigerant. If the on-off valve 32 is opened, only the number of rotations of the motor 2 is adjusted in step 14.

If the necessary number of rotations is more than the first number of rotations on the other hand, it is determined in step 16 whether the necessary number of rotations is equal to or more than the second number of rotations (e.g., 70 Hz). If the necessary number of rotations is equal to or more than the second number of rotations, it is determined in step 17 whether the on-off valve 32 is opened. If the on-off valve 32 is opened, in step 18, the on-off valve 32 is closed and the number of rotations of the motor 2 is adjusted to a value capable of obtaining the necessary flow rate of refrigerant. If the on-off valve 32 closed, only the number of rotations of the motor 2 is adjusted in step 19.

By carrying out the control described with reference to FIGS. 3A and 3B, the rotary compressor 100 can exert high efficiency also when low ability is required (when, is small) as shown by solid lines in FIG. 5. In FIG. 5, the rated ability of the rotary compressor 100 is defined as “100%”. If the rated ability is defined as a criterion, the efficiency of the rotary compressor 100 is lowered as the as ability to be exerted is reduced, i.e., as the number of rotations of the motor 2 is reduced. As shown by the broken lines, when the motor 2 is driven with the number of rotations which is 50% or less of the rated number of rotations, the efficiency is largely lowered. In this embodiment, when relatively low ability is required, the operation is carried out in the low volume mode with the suction volume V/2. According to this, the motor 2 can be driven with the number of rotations which is close to the rated number of rotations as close as possible. Therefore, even in a region where necessary ability is 50% or less of the rated ability, the rotary compressor 100 can exert excellent efficiency.

Third Embodiment

As shown in FIG. 6, a rotary compressor 300 of a third embodiment includes a control mechanism 30 having a structure different from that of the rotary compressor 100 of the first embodiment. Other structures are the same as those described in the first embodiment.

As the control mechanism 30, the rotary compressor 300 includes a communication passage 16, a three-way valve 90 and a high pressure path 92. The communication passage 16 is composed of an upstream portion 16h which brings the three-way valve 90 and an interior space 28 into communication with each other, and a downstream portion which brings the three-way valve 90 and a suction path 14 into communication with each other. The high pressure path 92 has one end connected to the three-way valve 90 and the other end connected to an oil reservoir 22. The high pressure path 92 is a path for supplying pressure which is equal to that of compressed refrigerant to an interior space 28. The rotary compressor 300 of this embodiment is a so-called high pressure shell type compressor in which an interior of a hermetic container 1 is filled with compressed refrigerant. Oil having pressure which is substantially equal to that of compressed refrigerant is held in the oil reservoir 22. The three-way valve 90 connects one of the suction path 14 and the high pressure path 92 to the upstream portion 16h of the communication passage 16. By controlling the three-way valve 90, the rotary compressor 300 can be operated in any of a high volume mode and a low volume mode.

In the low volume mode, the three-way valve 90 is controlled such that the suction path 14 is brought into communication with the upstream portion 16h of the communication passage 16. In this case, as a volume of the operation chamber 25 is reduced, a first check valve 35a opens, and refrigerant is discharged to outside of the operation chamber 25. The discharged refrigerant returns to the suction path 14 through the communication passage 16. Hence, pressure in the operation chamber 25 does not rise. At this time, since refrigerant is not discharged from the interior space 28 into the hermetic container 1, the rotary compressor 300 is operated with substantially zero suction volume.

In the high volume mode on the other hand, the three-way valve 90 is controlled such that the high pressure path 92 is brought into communication with the upstream portion 16h of the communication passage 16. In this case, since refrigerant does not return from the operation chamber 25 to the suction path 14 through the communication passage 16, pressure of oil in the oil reservoir 22 is introduced into the interior space 28. Hence, if a suction stroke of refrigerant is completed, a compression stroke of refrigerant is immediately started. At this time, compressed refrigerant is discharged into the interior space 28 through a first passage 34a. When pressure in the interior space 28 exceeds pressure in the hermetic container 1, a second check valve 35b opens and refrigerant is discharged into the hermetic container 1. At this time, the rotary compressor 300 is operated with a normal suction volume.

In this embodiment, it is preferable that a portion between the three-way valve 90 and the high pressure path 92 is composed of a capillary tube (not shown) or the like having a relatively small cross-sectional area as compared with the communication passage 16. Compressed refrigerant is discharged into the interior space 28 through the first passage 34a, but if refrigerant-passage resistance of the high pressure path 92 is large, the second check valve 35b smoothly opens, and refrigerant in the interior space 28 is discharged into the hermetic container 1.

In this embodiment, the high pressure path 92 has one end connected to (opened toward) the oil reservoir 22. To achieve a purpose of supplying high pressure to the interior space 28, the one end of the high pressure path 92 may be connected to any portion of the interior of the hermetic container 1. When the rotary compressor 300 is used in the refrigeration cycle apparatus, the high pressure path 92 may be connected to a high pressure portion (e.g., a portion between the rotary compressor 300 and a radiator) of the refrigerant circuit. However, in the embodiment, if the interior space is closed, a sealing effect by oil can be obtained. This is preferable to prevent efficiency from being deteriorated by leakage of refrigerant.

Although the three-way valve 90 is used as the control mechanism 30 in this embodiment, a four-way valve may be used.

More specifically, three ends of the four-way valve are connected to the high pressure path 92, the upstream portion 16h of the communication passage 16 which is in communication with the interior space 28, and the communication passage 16 which is in communication with the suction path 14, and remaining one end of the four-way valve is always closed. According to this configuration also, the same effect as that of the embodiment can be obtained.

Application Embodiment

As shown in FIG. 7, a refrigeration cycle apparatus 500 can be configured using the rotary compressor 100. The refrigeration cycle apparatus 500 includes the rotary compressor 100, a radiator 502, an expansion mechanism 504 and an evaporator 506. These devices are connected to one another in this order through refrigerant pipes to form a refrigerant circuit. The radiator 502 is composed of an air-refrigerant heat exchanger for example, and cools refrigerant which is compressed by the rotary compressor 100. The expansion mechanism 504 is composed of an expansion valve, and expands refrigerant which is cooled by the radiator 502. The evaporator 506 is composed of an air-refrigerant heat exchanger for example, and heats refrigerant which is expanded by the expansion mechanism 504. The rotary compressors 200 and 300 of the second and third embodiments may be used instead of the rotary compressor 100 of the first embodiment.

Some of the embodiments described in this specification can be combined together within a range not departing from the subject matter of the invention. For example, even if the on-off valve 30 described in the second embodiment is combined with the three-way valve 90 described in the third embodiment, the effect described in the second embodiment can be obtained.

INDUSTRIAL APPLICABILITY

The present invention is effective for a compressor of a refrigeration cycle apparatus which can be utilized for a water heater, a hydronic heater and an air conditioner. Especially, the invention is effective for a compressor of the air conditioner which requires wide ability.

ROTARY COMPRESSOR

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