EP2551526B1

EP2551526B1 - Two stage rotary compressor

Info

Publication number: EP2551526B1
Application number: EP12167431.1A
Authority: EP
Inventors: Atsuyoshi Fukaya; Masao Tani
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2011-07-28
Filing date: 2012-05-10
Publication date: 2019-05-01
Anticipated expiration: 2032-05-10
Also published as: JP2013029059A; EP2551526A3; CN102900669B; RU2012122456A; EP2551526A2; RU2501978C1; JP5586537B2; KR101376872B1; CN102900669A; KR20130014337A

Description

[Technical Field]

The present disclosure relates to a two stage rotary compressor with two compression units.

[Background Art]

Hitherto, there exists a two stage rotary compressor provided with two compression units (a low stage compression unit and a high stage compression unit) in a compression mechanism in which the low stage compression unit and the high stage compression unit are connected in series. In this kind of two stage rotary compressor, the low stage compression unit compresses refrigerant, which has been sucked in from a heat pump cycle, to a certain pressure (ultimate pressure). This ultimate pressure is determined by the configuration of the compression chamber volume of the low stage compression unit and the compression chamber volume of the high stage compression unit. The high stage compression unit further compresses the refrigerant that has been compressed in the low stage compression unit. Furthermore, in a case of an internal high-pressure type, two stage rotary compressor, the refrigerant that has been compressed in the high stage compression unit is discharged into an internal space of a hermetic vessel and is discharged into the heat pump cycle from the internal space of the hermetic vessel.
In a conventional internal high-pressure type, two stage rotary compressor, an intermediate passage is formed so as to pass around the exterior of the hermetic vessel in order to introduce the refrigerant of intermediate pressure that has been compressed in the low stage compression unit into the high stage compression unit.
However, the intermediate communication passage becomes exceedingly long in the conventional two stage rotary compressor that is formed with the intermediate passage that passes around the exterior of the hermetic vessel. As a result, followability becomes poor when the refrigerant in the intermediate passage is introduced into the high stage compression unit, and pressure pulsation is caused in the intermediate passage. Disadvantageously, a sufficient pressure pulsation suppressing effect cannot be obtained.
Thus, there has been proposed a conventional internal high-pressure type, two stage rotary compressor having an intermediate passage formed in a hermetic vessel.
As regards to conventional two stage rotary compressors, there has been proposed a two stage rotary compressor formed with a discharge space constituted in an intermediate passage partitioning a low stage compression unit and a high stage compression unit. Refrigerant with intermediate pressure (the refrigerant that has been discharged from the low stage compression unit) is discharged into the discharge space to prevent the refrigerant with intermediate pressure to be excessively discharged into the high stage compression unit (see, for example, Patent Literature 1).
Further, as regards to conventional two stage rotary compressors, there has been proposed a two stage rotary compressor provided with an intermediate passage in a compression mechanism by displacing phases of an inlet port of a high stage compression unit and an inlet port of a low stage compression unit (see, for example, Patent Literature 2).
Furthermore, as regards to conventional two stage rotary compressors, there has been proposed a two stage rotary compressor provided with an intermediate passage penetrating though a compression mechanism by disposing the intermediate passage between a vane slot and the low stage and high stage inlet passages (see, for example, Patent Literature 3).
WO 2011/055444 A1 is directed to a heat pump device, a two-stage compressor, and a method of operating a heat pump device. A two-stage compressor and a heat pump device using a two-stage compressor operate with improved efficiency when the load is low. A heat pump device is provided with a main refrigerant circuit formed by sequentially connecting by piping a two-stage compressor, a first heat exchanger, a first expansion mechanism, and a second heat exchanger. When the load is higher than a predetermined load, the two-stage compressor discharges to a refrigerant circuit a refrigerant compressed in two stages by a low-stage compression section and a high-stage compression section. When the load is lower than the predetermined load, the two-stage compressor causes the refrigerant compressed by the low-stage compression section to bypass the high-stage compression section without the refrigerant being compressed by the high-stage compression section and discharges the refrigerant to the main refrigerant circuit.

[Citation List]

[Patent Literature]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2000-87892
Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2007-113542
Patent Literature 3: Japanese Unexamined Patent Application Publication No. 2010-156226

[Summary of Invention]

[Technical Problem]

In a heat pump system (heat pump cycle) using a compressor, there are cases in which pressure of refrigerant discharged from the compressor (in other words, the pressure of the refrigerant flowing into a condenser) may be allowed to be low such as when the load is small. However, conventional two stage rotary compressors formed with an intermediate passage in the compression mechanism (see, for example, Patent Literature 1 to 3) have not taken into consideration small load operations such as above. Thus, the pressures of the refrigerant discharged from the two stage rotary compressors are higher than the desired pressure, resulting in over-compressed states. Accordingly, operating efficiencies of conventional two stage rotary compressors formed with an intermediate passage in the compression mechanism disadvantageously drop during small load operations.
Further, since the two stage rotary compressor described in Patent Literature 1 is formed with the discharge space in an intermediate plate, in which the discharge plate is discharged with the refrigerant of intermediate pressure, the distance between bearings of the compression mechanism (the distance between bearings that rotatably supports a drive shaft, in which the bearings are provided on an upper and lower end of the compression mechanism) becomes large. Accordingly, since in the two stage rotary compressor described in Patent Literature 1, the deflection of the compressor increases when the load of the refrigerant acts on the compression chamber, the reliability of the bearings is disadvantageously reduced.
Furthermore, since the two stage rotary compressor described in Patent Literature 2 displace phases of an inlet port of a high stage compression unit and an inlet port of a low stage compression unit, the compression efficiency disadvantageously drops due to the increase of dead volume in the compression chamber of the high stage compression unit.
In addition, since the installation area of the intermediate passage of the two stage rotary compressor described in Patent Literature 3 is small, limitation in the passage area of the intermediate passage occur and disadvantageously results in drop of efficiency due to pressure loss.
The present disclosure has been made to solve at least one of the above problems and an object thereof is to provide a two stage rotary compressor that is capable of improving the followability of the refrigerant introduced into the high stage compression unit, thus, suppressing the pressure pulsation in the intermediate passage, and, further, to provide an two stage rotary compressor that is capable of preventing drop of operating efficiency during low load operation.

[Solution to Problem]

A two stage rotary compressor according to the disclosure includes a hermetic vessel; a compression mechanism disposed in the hermetic vessel; an electric motor disposed in the hermetic vessel and being a driving source of the compression mechanism; and a drive shaft transmitting a driving force of the electric motor to the compression mechanism, the compression mechanism having a low stage frame, a low stage cylinder in which a first through hole that is be a low stage compression chamber is formed and in which one opening of the first through hole is occluded with the low stage frame, an intermediate partition plate that occludes the other opening of the first through hole, a high stage cylinder in which a second through hole that is to be a high stage compression chamber is formed and in which one opening of the second through hole is occluded with the intermediate partition plate, a high stage frame that occludes the other opening of the second through hole, a low stage rolling piston that is provided in an eccentric portion of the drive shaft, and performs an eccentric rotational motion in an interior of the low stage compression chamber, a high stage rolling piston that is provided in an eccentric portion of the drive shaft, the high stage rolling piston performing an eccentric rotational motion in an interior of the high stage compression chamber, a low stage vane partitioning the interior of the low stage compression chamber into a suction space and a compression space, and a high stage vane partitioning the interior of the high stage compression chamber into a suction space and a compression space, and a low stage compression unit and a high stage compression unit being formed by stacking, in order, the low stage frame, the low stage cylinder, the intermediate partition plate, the high stage cylinder, and the high stage frame. The two stage rotary compressor compresses a refrigerant sucked from a pipe connected to a low stage inlet port of the low stage compression chamber of the low stage compression unit, in the low stage compression chamber, recompressing the refrigerant introduced into the high stage compression chamber through an intermediate passage, and discharging the refrigerant compressed at the high stage compression chamber to a discharge pressure space that is an internal space of the hermetic vessel.
In the two stage rotary compressor, a low stage outlet port discharging the refrigerant that is compressed in the low stage compression chamber is formed in the low stage frame, a low stage cover covering the low stage outlet port is provided, the low stage cover forming a low stage discharge space therein, the intermediate passage is formed penetrating through the low stage frame, the low stage cylinder, and the intermediate partition plate, the intermediate passage connecting the low stage discharge space and the high stage compression chamber, and a bypass mechanism provided in the low stage cover opens to connect the low stage discharge space and the discharge pressure space when a load is smaller than a predetermined load.

[Advantageous Effects of Invention]

The two stage rotary compressor according to the present disclosure forms the intermediate passage in the compression mechanism without extending the intermediate passage outside the hermetic vessel, and, thus, is capable of shortening the intermediate passage. Accordingly, the followability of the refrigerant introduced into the high stage compression unit can be improved and pressure pulsation in the intermediate passage can be suppressed.
Furthermore, the two stage rotary compressor according to the present disclosure is equipped with a bypass mechanism that opens when the load is smaller than a predetermined load and that connects the low stage discharge space to the discharge pressure space. Accordingly, the refrigerant that has been compressed by the low stage compression unit can be bypassed and discharged into the heat pump cycle without being compressed by the high stage compression unit during low load operation. Thus, the two stage rotary compressor according to the present disclosure is capable of reducing the over compression loss generated during low load operation and prevent drop of operating efficiency during low load operation.

[Brief Description of Drawings]

Fig. 1 is a longitudinal sectional view illustrating a two stage compressor according to Embodiment of the present disclosure.
Fig. 2 is a cross-sectional view taken along the line A-A of Fig. 1.
Fig. 3 is a cross-sectional view taken along the line B-B of Fig. 1.
Fig. 4 is a cross-sectional view taken along the line C-C of Fig. 1.
Fig. 5 is a cross-sectional view taken along the line D-D of Fig. 1.
Fig. 6 is a cross-sectional view taken along the line E-E of Fig. 1.
Fig. 7 is a diagram comparing an operating efficiency of the two stage compressor according to Embodiment and a conventional two stage rotary compressor.

[Description of Embodiments]

Embodiment

A configuration of an explanatory two stage rotary compressor (two stage compressor 100) according to the disclosure will be described subsequently.
Fig. 1 is a longitudinal sectional view illustrating a two stage compressor according to Embodiment of the disclosure. Further, Fig. 2 is a cross-sectional view taken along the line A-A of Fig. 1, Fig. 3 is a cross-sectional view taken along the line B-B of Fig. 1, Fig. 4 is a cross-sectional view taken along the line C-C of Fig. 1, Fig. 5 is a cross-sectional view taken along the line D-D of Fig. 1, and Fig. 6 is a cross-sectional view taken along the line E-E of Fig. 1. Note that in order to facilitate the understanding of the configuration of the two stage compressor 100, Fig. 1 is a diagram with combined cross-sectional areas sectioned in a plurality of positions. Accordingly, accurate positions of each component in planar view or bottom view will be the positions illustrated in Fig. 2 to Fig. 6.
The two stage compressor 100 according to Embodiment includes two compression units (a low stage compression unit 10 and a high stage compression unit 30) in a compression mechanism 3. This two stage compressor 100 includes an electric motor 2 (motor unit), the low stage compression unit 10, the high stage compression unit 30, a low stage cover 19, a high stage cover 39, a low stage frame 14, a high stage frame 34, an intermediate partition plate 50, a drive shaft 4, and the like. Specifically, in a hermetic vessel 1, disposed in the order from bottom to top are the high stage cover 39, the high stage frame 34, the high stage compression unit 30, the intermediate partition plate 50, the low stage compression unit 10, the low stage frame 14, the low stage cover 19, and the electric motor 2. Further, the drive shaft 4 is provided along the vertical direction of the hermetic vessel 1, and in the bottom portion of the hermetic vessel (that is, at the lower end portion of the drive shaft 4), a lubricant oil storing portion 6 retaining lubricant oil 6a is formed, This lubricant oil 6a lubricates the compression mechanism 3, the bearings, and the like.
The low stage compression unit 10 of the compression mechanism 3 includes a low stage cylinder 11, a low stage rolling piston 12, a low stage vane 26 (see Fig. 4), and the like. The low stage cylinder 11 is substantially plate shaped and has a through hole with a substantially cylindrical geometry formed in the substantially center portion that serves as a low stage compression chamber 15. The upper opening of this through hole is occluded with the low stage frame 14 and the bottom opening is occluded with an intermediate partition plate 50 defining the low stage compression chamber 15. Further, in the low stage compression chamber 15, a low stage inlet port 21 and a low stage outlet port 16 formed in the low stage frame 14 are in communication. The low stage inlet port 21 is connected to an inlet pipe 8 via a connecting pipe 9 and an inlet muffler 7 that are provided outside the hermetic vessel 1. That is, the low stage inlet port 21 is connected to the low-pressure side of the heat pump cycle. Furthermore, the low stage outlet port 16 is provided with a reed valve that is a plate shaped low stage discharge valve 17 and a low stage valve guard 18 mounted with a rivet 18a (see Fig. 3). By pushing up the low stage discharge valve 17 of the reed valve and opening the low stage outlet port 16, the low stage compression chamber 15 is allowed to communicate with a low stage discharge space 20 that will be described subsequently.
The low stage compression chamber 15 is provided with the low stage rolling piston 12 and the low stage vane 26. The low stage rolling piston 12 has a substantially cylindrical geometry and is provided to the eccentric portion of the drive shaft 4. The low stage vane 26 is slidably provided in the low stage vane slot 27 formed in the low stage cylinder 11. Further, the low stage vane 26 is energized towards the drive shaft 4 with an energizing member such as a spring in which the tip of the low stage vane 26 is capable of following the periphery of the low stage rolling piston 12. As such, the low stage compression chamber 15 is separated into a suction space in communication with the low stage inlet port 21 and a compression space in communication with the low stage outlet port 16. As can be understood from Fig. 3 and Fig. 4, the low stage inlet port 21 of the low stage compression chamber 15 is in communication with the low stage compression chamber 15 in the vicinity of the left side of the low stage vane 26 when viewed in planar view. Further, the low stage outlet port 16 is in communication with the low stage compression chamber 15 in the vicinity of the right side of the low stage vane 26 when viewed in planar view.
The high stage compression unit 30 includes a high stage cylinder 31, a high stage rolling piston 32, a high stage vane 42 (see Fig. 5), and the like. The high stage cylinder 31 is substantially plate shaped and has a through hole with a substantially cylindrical geometry formed in the substantially center portion that serves as a high stage compression chamber 35. The upper opening of this through hole is occluded with the intermediate partition plate 50 and the bottom opening is occluded with the high stage frame 34 defining the high stage compression chamber 35. The high stage compression chamber 35 is formed so as to have a smaller volume than the low stage compression chamber 15. Further, in the high stage compression chamber 35, a high stage inlet port 41 formed in the high stage cylinder 31 and a high stage outlet port 36 formed in the high stage frame 34 are in communication with each other. The high stage inlet port 41 of the high stage compression unit 30 is capable of communicating with the low stage outlet port 16 of the low stage compression unit 10 via the subsequently described low stage discharge space 20 and the intermediate passage 51. Furthermore, the high stage outlet port 36 is provided with a reed valve that is a plate shaped high stage discharge valve 37 and a high stage valve guard
38 mounted with a rivet 38a (see Fig. 6), By pushing up the high stage discharge valve 37 of the reed valve and opening the high stage outlet port 36, the high stage compression chamber 35 is allowed to communicate with a high stage discharge space 40 that will be described subsequently.
The high stage compression chamber 35 is provided with the high stage rolling piston 32 and the high stage vane 42. The high stage rolling piston 32 has a substantially cylindrical geometry and is provided to the eccentric portion of the drive shaft 4. In Embodiment, the high stage rolling piston 32 is at a substantially opposite phase (a position rotated by substantially 180 degrees around the rotation shaft of the drive shaft 4) to the low stage rolling piston 12 when in planar view. The high stage vane 42 is slidably provided in the high stage vane slot 43 formed in the high stage cylinder 31. Further, the high stage vane 42 is energized towards the drive shaft 4 with an energizing member such as a spring in which the tip of the high stage vane 42 is capable of following the periphery of the high stage rolling piston 32. As such, the high stage compression chamber 35 is separated into a suction space in communication with the high stage inlet port 41 and a compression space in communication with the high stage outlet port 36. As can be understood from Fig. 5 and Fig. 6, the high stage inlet port 41 is in communication with the high stage compression chamber 35 in the vicinity of the left side of the high stage vane 42 when viewed in planar view. Further, the high stage outlet port 36 is in communication with the high stage compression chamber 35 in the vicinity of the right side of the high stage vane 42 when viewed in planar view.
Furthermore, as can be understood from Fig. 3 to 6, the low stage inlet port 21 of the low stage compression chamber 15 and the high stage inlet port 41 of the high stage compression chamber 35 are substantially in the same phase when in planar view. The low stage outlet port 16 and the high stage outlet port 36 are substantially in the same phase when in planar view. Accordingly, the two stage compressor 100 according to Embodiment is different to the two stage rotary compressor described in Patent Literature 2 such that the dead volume in the high stage compression chamber 35 does not increase and the compression efficiency does not drop.
The low stage frame 14 includes an upper bearing and rotatably supports the substantially middle portion of the drive shaft 4. In the low stage frame 14, as mentioned above, the low stage outlet port 16 of the low stage compression unit 10 is formed. The low stage cover 19 is a cup-shaped vessel with its opening in the lower portion. This low stage cover 19 is provided so as to cover the low stage outlet port 16 from above and forms a low stage discharge space 20 therein.
Further, the intermediate passage 51 is also in communication with the low stage discharge space 20. This intermediate passage 51 penetrates through the low stage frame 14, the low stage cylinder 11, and the intermediate partition plate 50 in the vertical direction and connects the low stage discharge space 20 and the high stage inlet port 41. That is, the refrigerant that has flowed into the low stage discharge space 20 is sucked into the high stage compression unit 30 through the intermediate partition plate 50.
Note that in penetrating through the low stage cylinder 11, this intermediate passage 51 penetrates through a position that is on the left side of the low stage vane 26 that is a position farther away from the lower stage vane 26 (that is, the low stage vane slot) than the low stage inlet port 21. In other words, as the central axis of the drive shaft 4 as a reference point, when assuming that the direction of rotation from the low stage vane 26 to the low stage inlet port 21 on the short distance side is to be referred to as a forward direction (the direction indicated by an arrow in Fig. 4), the intermediate passage 51 is formed more downstream than the low stage inlet port 21 in the forward direction.
The high stage frame 34 includes a lower bearing and rotatably supports the lower end portion of the drive shaft 4. In the high stage frame 34, as mentioned above, the high stage outlet port 36 of the high stage compression unit 30 is formed. The high stage cover 39 is a cup-shaped vessel with its opening in the upper portion. This low stage cover 39 is provided so as to cover the high stage outlet port 36 from below and forms the high stage discharge space 40 therein.
Further, a discharge passage 52 in communication with the internal space of the hermetic vessel 1 is formed in the high stage discharge space 40. This discharge passage 52 penetrate through the high stage frame 34, the high stage cylinder 31, the intermediate partition plate 50, the low stage cylinder 11, and the low stage frame 14 in the vertical direction and connects the high stage discharge space 40 and the internal space of the hermetic vessel 1. That is, the two stage compressor 100 according to Embodiment is an internal high-pressure type compressor in which inside the hermetic vessel 1 becomes a discharge pressure space 53 (during steady operation, the space having the pressure of the high-pressure refrigerant discharged from the high stage compression unit 30). For example, the discharge pipe 5 is provided in the upper portion of the hermetic vessel 1 and the high-pressure refrigerant that has been discharged into the hermetic vessel 1 is discharged to the outside from this discharge pipe 5. Note that, in planar view, this discharge passage 52 penetrates through a position that is point symmetry to the intermediate passage 51 when the central axis of the drive shaft 4 is given as a reference point.
The electric motor 2 is a driving source for the low stage compression unit 10 and the high stage compression unit 30. This electric motor 2 includes a stator 2a and a rotor 2b. The stator 2a has a substantially cylindrical geometry and is fixed to an inner circumference of the hermetic vessel 1. The rotor 2b has a substantially cylindrical geometry and is disposed in an inner circumference of the stator 2a with a predetermined gap therewith. Further, the upper end of the drive shaft 4 is fixed into the inner circumference of the rotor 2b.
Furthermore, the two stage compressor 100 according to Embodiment is provided with an injector 60 in the low stage cover 19. One end of this injector 60 is opened to the low stage discharge space 20 and the other end is connected to an injection pipe 61. Note that the injector 60 is for injecting refrigerant in the heat pump cycle other than the two stage compressor 100 into the refrigerant that has been discharged from the low stage compression unit 10. Accordingly, the connecting position of the injector 60 is not limited to the low stage cover 19, but may be any connecting position is in the passage (low stage discharge space) before the refrigerant that has been discharged from the low stage compression unit 10 is sucked into the high stage compression unit 30.
Additionally, the two stage compressor 100 according to Embodiment has a bypass port 23 formed in the low stage cover 19 in which the bypass port 23 connects the low stage discharge space 20 and the discharge pressure space 53 that is the internal space of the hermetic vessel 1. Furthermore, the bypass port 23 is provided with a reed valve that is a plate shaped bypass valve 24 and a bypass valve guard 25 mounted with a rivet 29 (see Fig. 2). These will be referred to as a bypass mechanism.
Note that in Embodiment, the positional relation of the bypass port 23 and the intermediate passage 51 is as shown in Fig,2. In other words, as the central axis of the drive shaft 4 as a reference point, when assuming that the direction of rotation from the low stage outlet port 16 to the bypass port 23 on the short distance side is to be referred to as a forward direction (the direction indicated by an arrow in Fig. 2), the intermediate passage 51 is formed more downstream than the bypass port 23 in the forward direction.
Next, operation of the two stage compressor 100 will be described.
When electric power is supplied, the electric motor 2 operates. The electric motor 2 and the compression mechanism 3 are connected by the drive shaft 4 and the motive power that is generated by the electric motor 2 is transmitted to the compression mechanism 3 through the drive shaft 4. Specifically, when supplied with electric power, the rotor 2b of the electric motor 2 rotates. When the rotor 2b rotates, the drive shaft 4 that is fitted into the rotor 2b also rotates. Further, when the drive shaft 4 rotates, the low stage rolling piston 12 and the high stage rolling piston 32, which are fitted into the drive shaft 4, each eccentrically rotates in the low stage compression chamber 15 and the high stage compression chamber 35, respectively. With the eccentric rotation of the low stage rolling piston 12 and the high stage rolling piston 32, refrigerant in the low stage compression unit 10 and the high stage compression unit 30 are compressed.
In the two stage compressor 100 that operates as above, the refrigerant flows as follows.
First, a low-pressure refrigerant flows into the inlet muffler 7 from the outside through the suction pipe 8. The low-pressure refrigerant that has flowed into the inlet muffler 7 is sucked into the low stage compression chamber 15 through the connecting pipe 9. The low-pressure refrigerant that has been sucked into the low stage compression chamber 15 is compressed to an intermediate pressure in the low stage compression chamber 15. When the refrigerant is compressed to an intermediate pressure, the low stage discharge valve 17 opens due to the pressure difference between the refrigerant in the low stage compression chamber 15 and the refrigerant in the low stage discharge space 20, and the refrigerant in the low stage compression chamber 15 is discharged from the low stage outlet port 16 to the low stage discharge space 20. Here, the intermediate pressure is a pressure that is determined by a ratio between the volume of the suction chamber of the low stage compression chamber 15 and the volume of the suction chamber of the high stage compression chamber 35.
The intermediate-pressure refrigerant that has been discharged into the low stage discharge space 20 is sucked into the high stage compression chamber 35 through the intermediate passage 51. The intermediate-pressure refrigerant that has been sucked into the high stage compression chamber 35 is compressed to a discharge pressure in the high stage compression chamber 35. When the refrigerant is compressed to a discharge pressure, the high stage discharge valve 37 opens due to the pressure difference between the refrigerant in the high stage compression chamber 35 and the refrigerant in the high stage discharge space 40, and the refrigerant in the high stage compression chamber 35 is discharged from the high stage outlet port 36 to the high stage discharge space 40. The refrigerant with the discharge pressure that has been discharged to the high stage discharge space 40 is discharged into the discharge pressure space 53 in the upper direction of the low stage compression unit 10 through the discharge passage 52. Then, the refrigerant with the discharge pressure that has been discharged to the discharge pressure space 53 is discharged to the outside from the discharge pipe 5.
Note that when an injection operation is carried out in the heat pump system that is equipped with the two stage compressor 100 (a heat pump cycle using the two stage compressor 100), injection refrigerant is injected into the low stage discharge space 20 from the injection pipe 61 through the injector 60 that are shown in Fig. 1. The injection refrigerant is mixed with the intermediate-pressure refrigerant, which has been discharged from the low stage compression chamber 15, in the low stage discharge space 20 and is compressed in the high stage compression unit 30.
When the load of the heat pump system is small (hereinafter also referred to as "during low load operation"), there are cases in which an over-compressed state occurs which is a state in which compression of the low stage compression unit 10 alone reaches the discharge pressure (in other words, the pressure in which the refrigerant flows into the condenser). That is, there are cases in which the intermediate pressure of the refrigerant mentioned above becomes higher than the required discharge pressure. In these cases, the two stage compressor 100 according to Embodiment is configured such that the bypass valve 24 opens by the pressure difference between the refrigerant of the low stage discharge space 20 and refrigerant of the discharge pressure space 53 and that the refrigerant in the low stage discharge space 20 is discharged into the discharge pressure space 53 through the bypass port 23. In other words, the two stage compressor 100 according to Embodiment is configured such that the bypass valve 24 deforms itself and opens the bypass port 23 when the pressure in the low stage discharge space 20 becomes equal to or higher than the pressure of the discharge pressure space 53 by a predetermined value. That is, the refrigerant that has been discharged from the low stage compression unit 10 to the low stage discharge space 20 is bypassed and discharged into the discharge pressure space 53 without being compressed in the high stage compression unit 30.
When in an over-compressed state, the discharge pressure is reached by the compression of the low stage compression unit 10 alone and compression by the high stage compression unit 30 becomes a waste, and efficiency drops when compression is carried out by the high stage compression unit 30. However, in the two stage compressor 100, when in an over-compressed state, the refrigerant that has been compressed in the low stage compression unit 10 bypasses the high stage compression unit 30 and is discharged. Thus, loss (over compression loss) caused when an over compression state occurs can be suppressed and operating efficiency during low load operation can be improved.
Furthermore, the two stage compressor 100 according to Embodiment is provided with a bypass port 23 in the low stage cover 19. Accordingly, the refrigerant that is discharged from the bypass port 23 to the discharge pressure space 53 is discharged into the discharge pressure space 53 in the hermetic vessel 1 without passing through the intermediate passage 51. That is, the refrigerant that is discharged from the bypass port 23 to the discharge pressure space 53 is discharged into the discharge pressure space 53 from the bypass port 23 without compression loss caused by passing through the intermediate passage 51. Thus, over compression loss can be effectively suppressed during low load operation.
Note that as mentioned above, a lubricant oil storing portion 6 is formed on the bottom side of the hermetic vessel 1 and lubricant oil 6a is enclosed therein. Since the lubricant oil 6a is supplied to the machine parts of the compression mechanism 3, an amount that can at least immerse the compression unit disposed on the upper side (the low stage compression unit 10 in Fig. 1) is enclosed. In a typical two stage rotary compressor (see Patent Literature 1 to 3), when the two stage rotary compressor is placed longitudinally, the low stage compression unit is provided below the high stage compression unit. Accordingly, as in the two stage rotary compressors described in Patent Literature 2 and 3, that is, in the two stage rotary compressor that discharges the refrigerant that has been compressed in the low stage compression unit into the low stage cover (low stage discharge space), the low stage discharge space is provided below the low stage compression unit. That is, the low stage cover is provided on the lower side of the low stage compression unit. Thus, the low stage cover is immersed in the lubricant oil. In this case, when attempting to form a bypass port 23 according to the Embodiment in the low stage cover, the lubricant oil intrudes into the low stage discharge space from the bypass port 23. Further, the lubricant oil is drawn up when the refrigerant is discharged from the bypass port 23, and outflow of the lubricant oil from the two stage rotary compressor is disadvantageously increased. Because of this, it is not possible to form a bypass port 23 according to Embodiment in the low stage cover in a typical two stage rotary compressor. Therefore, in the two stage rotary compressors described in Patent Literature 2 and 3, when the two stage rotary compressor is placed longitudinally, there is no choice but to provide the bypass port 23 in the narrow and thin passage that connects the low stage discharge space and the high stage compression unit.
However, in the two stage compressor 100 according to Embodiment, when placing the two stage compressor 100 longitudinally, in contrast to typical ones, the low stage compression unit 10 is provided on the upper side of the high stage compression unit 30. Accordingly, the low stage discharge space 20 is provided on the upper side of the low stage compression unit 10, and the low stage cover 19 can be at a height where the low stage cover 19 is not immersed in the lubricant oil 6a. As a result, the bypass port 23 can be provided in the low stage cover 19.
Further, in the two stage compressor 100 according to Embodiment, since the bypass port 23 is provided not in the intermediate passage 51 but in the low stage cover 19, the bypass valve 24 may be a reed valve with a simple structure. Accordingly, it will be possible to use the same parts that are used in the low stage discharge valve 17 and low stage valve guard 18, and high stage discharge valve 37 and high stage valve guard 38 for the bypass valve 24 and the bypass valve guard 25. By sharing the same parts, cost can be suppressed to a low level. Furthermore, since the structure of the bypass valve 24 is simple, it will be possible to suppress the assembling cost to a low level.
Next, the features of the intermediate passage 51 of the two stage compressor 100 according to Embodiment will be described.
As mentioned above, the intermediate passage 51 penetrates through the low stage frame 14, the low stage cylinder 11, and the intermediate partition plate 50 in the vertical direction and connects the low stage discharge space 20 and the high stage inlet port 41. That is, the refrigerant that has been compressed in the low stage compression unit 10 flows into the intermediate passage 51 after being discharged into the low stage discharge space 20. Accordingly, different to the two stage rotary compressor described in Patent Literature 1, the discharge space for the low stage compression unit 10 does not need to be formed in the intermediate partition plate 50. Thus, different to the two stage rotary compressor described in Patent Literature 1, the two stage compressor 100 according to Embodiment can shorten the distance between the low stage frame 14, which functions also as a bearing for the drive shaft 4, and the high stage frame 34, and increase the reliability of the two stage compressor 100 (specifically, the reliability of the low stage frame 14 and the high stage frame 34).
Further, the intermediate passage 51 is formed in a position farther away from the low stage vane 26 than the low stage inlet port 21 (in other words, the low stage vane slot 27), that is, a position that is not between the low stage inlet port 21 and the low stage vane 26 (in other words, the low stage vane slot 27). Accordingly, different to the intermediate passage described in Patent Literature 3, the intermediate passage 51 according to Embodiment can secure a large passage area and eliminate the main cause of the pressure loss resulting in drop of efficiency. Furthermore, since the intermediate passage 51 does not interfere with the low stage inlet port 21 and the low stage vane 26 (in other words, the low stage vane slot 27), the installation flexibility of the passage is increased. Note that although an intermediate passage 51 having an opening with a substantially cylindrical geometry is shown in Fig. 4 and other figures, any opening shape with a larger area than the low stage outlet port 16 may be employed.
Depending on the amount of refrigerant and the largeness/smallness of density of the refrigerant flowing into the intermediate passage, pressure pulsation occurs. In particular, in an inverter controlled two stage rotary compressor, pressure pulsation tends to occur due to the increase and decrease of the rotation speed. In the conventional two stage rotary compressor that disposes the intermediate passage outside the hermetic vessel, since the followability of the refrigerant that is introduced into the high stage compression unit is poor, in order to rid of the pressure pulsation in the intermediate passage by resonance, passage pipes with various pipe lengths need to be configured. However, since the two stage compressor 100 according to Embodiment provides the intermediate passage 51 in the compression mechanism 3 and shortens the passage length, the followability of the refrigerant introduced in the high stage compression unit 30 from the low stage compression unit 10 is improved and pressure pulsation is suppressed, and, thus, operating efficiency can be improved.
As mentioned above, as the central axis of the drive shaft 4 as a reference point, when assuming that the direction of rotation from the low stage outlet port 16 to the bypass port 23 on the short distance side is to be referred to as a forward direction (the direction indicated by an arrow in Fig. 2), the intermediate passage 51 is formed more downstream than the bypass port 23 in the forward direction. This forward direction is the main stream direction of the refrigerant flowing from the low stage outlet port 16 to the bypass port 23. By disposing the bypass port 23 and the intermediate passage 51 with such a positional relation, the refrigerant in an over-compressed state that has been discharged from the low stage compression unit 10 is discharged into the hermetic vessel through the bypass port 23 before reaching the intermediate passage 51 by means of the bypass mechanism (bypass port 23, bypass valve 24, and bypass valve guard 25). Accordingly, the refrigerant that has been discharged into the discharge pressure space 53 is reliably discharged into the discharge pressure space without passing through the intermediate passage 51, and the advantageous effect of the bypass mechanism increases. On the other hand, even if the conventional two stage rotary compressor, which disposes the intermediate passage outside the hermetic vessel 1, is provided with the bypass mechanism (the bypass mechanism provided in the low stage cover), since the passage length of the intermediate passage is long, the refrigerant in the over-compressed state cannot be discharged fully from the bypass port 23, and a portion of the refrigerant in the over-expanded state flows into the high stage compression unit causing unnecessary compression, resulting in drop of efficiency.
Last of all, improvement effect of the operating efficiency of the two stage compressor 100 according to Embodiment will be described.
Fig. 7 is a diagram comparing an operating efficiency of the two stage compressor according to Embodiment and the conventional two stage rotary compressor. Note that the conventional two stage rotary compressor in Fig. 7 is an internal high-pressure type, two stage rotary compressor, which disposes the intermediate passage outside the hermetic vessel, and is not provided with the bypass mechanism such as the one in Embodiment. Further, the operating efficiency of the two stage compressor 100 according to Embodiment is indicated with the operating efficiency of the conventional two stage rotary compressor as a reference (100%).
When comparing the operating efficiency during steady operation (the rated condition shown in Fig. 7), the operating efficiency of the two stage compressor 100 according to Embodiment is 102%, and the operating efficiency is improved by about 2% compared to the conventional two stage rotary compressor. From this result, it is understood that by forming the intermediate passage 51 in the compression mechanism 3, the followability of the refrigerant introduced into the high stage compression unit 30 is improved and pressure pulsation in the intermediate passage can be suppressed, leading to improvement of the operating efficiency.
When comparing the operating efficiency during low load operation (the low load condition shown in Fig. 7), the operating efficiency of the two stage compressor 100 according to Embodiment is 101.5%, and the operating efficiency is improved by about 1.5% compared to the conventional two stage rotary compressor. From this result, it is understood that in the two stage compressor 100 according to Embodiment, by providing a bypass mechanism (bypass port 23, bypass valve 24, and bypass valve guard 25) in the low stage cover 19, when in an over-compression state, it is possible to bypass the high stage compression unit 30 and discharge the refrigerant that has been compressed in the low stage compression unit 10, and thus improve the operating efficiency.
Note that in the two stage compressor 100 that is formed with the intermediate passage 51 in the compression mechanism 3, since the component being the intermediate passage does not protrude from the hermetic vessel 1, advantageous effect such as miniaturization, ease of packing and transportation, ease of disassembling, and the like can be obtained.

[Reference Signs List]

1. hermetic vessel; 2. electric motor; 2a. stator; 2b. rotor; 3. compression mechanism; 4. drive shaft; 5. discharge pipe; 6. lubricant oil storing portion; 6a. lubricant oil; 7. inlet muffler; 8. suction pipe; 9. connecting pipe; 10. low stage compression unit; 11. low stage cylinder; 12. low stage rolling piston; 14. low stage frame; 15. low stage compression chamber; 16. low stage outlet port; 17. low stage valve; 18. low stage valve guard; 18a. rivet; 19. low stage cover; 20. low side discharge space; 21. low stage inlet port; 23. bypass port; 24. bypass valve; 25. bypass valve guard; 26. low stage vane; 27. low stage vane slot; 29. rivet; 30. high stage compression unit; 31. high stage cylinder; 32. high stage rolling piston; 34. high stage frame; 35. high stage compression chamber; 36. high stage outlet port; 37. high stage valve; 38. high stage valve guard; 38a. rivet; 39. high stage cover; 40. high stage discharge space; 41. high stage inlet port; 42. high stage vane; 43. high stage vane slot; 50. intermediate partition plate; 52. discharge passage; 53. discharge pressure space; 60. injector; 61. injection pipe; 100. two stage compressor.

Claims

A two stage rotary compressor (100), comprising:
a hermetic vessel (1);

a compression mechanism (3) disposed in the hermetic vessel (1);

an electric motor (2) disposed in the hermetic vessel (1) and being a driving source of the compression mechanism (3); and

a drive shaft (5) transmitting a driving force of the electric motor (2) to the compression mechanism (3),

the compression mechanism (3) including

a low stage frame (14),

a low stage cylinder (11) in which a first through hole that is to be a low stage compression chamber (15) is formed and in which one opening of the first through hole is occluded with the low stage frame (14),

an intermediate partition plate (50) that occludes the other opening of the first through hole,

a high stage cylinder (31) in which a second through hole that is to be a high stage compression chamber (35) is formed and in which one opening of the second through hole is occluded with the intermediate partition plate (50),

a high stage frame (34) that occludes the other opening of the second through hole,

a low stage rolling piston (12) that is provided in an eccentric portion of the drive shaft (5), and performs an eccentric rotational motion in an interior of the low stage compression chamber (15),

a high stage rolling piston (32) that is provided in an eccentric portion of the drive shaft (5), and performs an eccentric rotational motion in an interior of the high stage compression chamber (35),

a low stage vane (26) partitioning the interior of the low stage compression chamber (15) into a suction space and a compression space, and

a high stage vane (42) partitioning the interior of the high stage compression chamber (35) into a suction space and a compression space, and

a low stage compression unit (10) and a high stage compression unit (30) being formed by stacking on the drive shaft (4) in order, the low stage frame (14), the low stage cylinder (11), the intermediate partition plate (50), the high stage cylinder (31), and the high stage frame (34),

the two stage rotary compressor compressing a refrigerant sucked from a pipe connected to a low stage inlet port (21) of the low stage compression chamber (15) of the low stage compression unit (10), in the low stage compression chamber (15), recompressing the refrigerant introduced into the high stage compression chamber (35) through an intermediate passage (51), and discharging the refrigerant compressed at the high stage compression chamber (35) to a discharge pressure space (53) that is an internal space of the hermetic vessel (1),

wherein,

a low stage outlet port (16) discharging the refrigerant that is compressed in the low stage compression chamber (15) is formed in the low stage frame (14),

a low stage cover (19) covering the low stage outlet port (16) is provided, the low stage cover (19) forming a low stage discharge space therein,

a bypass mechanism provided in the low stage cover (19) opens to connect the low stage discharge space and the discharge pressure space (53) when a load is smaller than a predetermined load,

the two-stage rotary compressor (100) being characterised in that

the intermediate passage (51) is formed penetrating through the low stage frame (14), the low stage cylinder (11), and the intermediate partition plate (50), the intermediate passage (51) connecting the low stage discharge space and the high stage compression chamber (35).
The two stage rotary compressor (100) of claim 1, wherein the bypass mechanism opens when a pressure of the low stage discharge space becomes, by a predetermined value, equal to or higher than a pressure of the discharge pressure space (53).
The two stage rotary compressor (100) of claim 2, wherein
in the compression mechanism (3), the low stage compression unit (10) is disposed above the high stage compression unit (30), and
the bypass mechanism includes
a bypass port (23) formed in the low stage cover (19),
a valve provided so as to occlude the bypass port (23), the valve deforming itself and opening the bypass port (23) when a pressure equal to or higher than a predetermined value is applied to the valve.
The two stage rotary compressor (100) of any one of claims 1 to 3, wherein when the central axis of the drive shaft (5) is assumed as a reference point and a direction of rotation from the low stage outlet port (16) to the bypass mechanism with shorter distance is to be referred to as a forward direction,
an opening of the intermediate passage to the low stage discharge space is formed more downstream than the bypass mechanism in the forward direction.
The two stage rotary compressor (100) of any one of claims 1 to 4, wherein a pipe (61) injecting refrigerant into the low stage discharge space is connected.
The two stage rotary compressor (100) of any one of claims 1 to 5, wherein a refrigerant inlet position of the low stage compression chamber (15) and a refrigerant inlet position of the high stage compression chamber (35) are substantially in the same phase.
The two stage rotary compressor (100) of any one of claims 1 to 6, wherein when the central axis of the drive shaft (5) is assumed as a reference point and a direction of rotation from the low stage vane (26) to the inlet port with shorter distance is to be referred to as a forward direction,
the intermediate passage is formed more downstream than the inlet port in the forward direction.