JPWO2012042894A1 - Positive displacement compressor - Google Patents

Abstract

The rotary compressor 100 includes a compression mechanism 3, a motor 2, a suction path 14, a return path 16, a variable volume mechanism 30, an inverter 42, and a control unit 44. The return path 16 plays a role of returning the working fluid from the working chamber 25 to the suction path 14. The variable volume mechanism 30 is provided in the return path 16 and allows the working fluid to return from the working chamber 25 to the suction path 14 through the return path 16 when the suction volume of the compression mechanism 3 should be relatively small. When the volume should be relatively large, the working fluid is prohibited from returning from the working chamber 25 to the suction passage 14 through the return passage 16. The variable volume mechanism 30 and the inverter 42 are controlled so as to compensate for the decrease in the suction volume by the increase in the rotation speed of the motor 2.

Description

  The present invention relates to a positive displacement compressor.

  The motor of the compressor is usually controlled by an inverter and a microcomputer. If the number of rotations of the motor is lowered, the refrigeration cycle apparatus using the compressor can be operated with a sufficiently lower capacity than the rating. Patent Document 1 further provides one technique for operating the refrigeration cycle apparatus with such a low capacity that cannot be realized by inverter control.

  FIG. 19 is a configuration diagram of the air-conditioning apparatus described in Patent Document 1. The compressor 915, the four-way valve 917, the indoor heat exchanger 918, the decompressor 919, and the outdoor heat exchanger 920 constitute a refrigeration cycle. The cylinder of the compressor 915 is provided with an intermediate discharge port that opens from the start to the middle of the compression stroke. The intermediate discharge port is connected to the suction path of the compressor 915 by a bypass path 923. The bypass 923 is provided with a flow control device 921 and an electromagnetic on-off valve 922. The electromagnetic on-off valve 922 is opened only during operation at a low set frequency. Thereby, the driving | running with a lower capability is attained.

JP-A 61-184365

  By the way, a shortcut for increasing the efficiency of the refrigeration cycle apparatus is to increase the efficiency of the compressor. The efficiency of the compressor is highly dependent on the efficiency of the motor used. Many motors are designed to exhibit the highest efficiency at a rotational speed in the vicinity of a rated rotational speed (for example, 60 Hz). Therefore, if the motor is driven at an extremely low number of revolutions, improvement in the efficiency of the compressor cannot be expected.

  In view of such circumstances, an object of the present invention is to provide a positive displacement compressor that can exhibit high efficiency even when low capacity is required (when the load is small).

That is, the present invention
A compression mechanism having a working chamber;
A motor for moving the compression mechanism;
A suction path for leading the working fluid to be compressed to the working chamber;
A return path for returning the working fluid from the working chamber to the suction path;
When the suction volume of the compression mechanism, which is provided in the return path, should be relatively small, the working fluid is allowed to return from the working chamber to the suction path through the return path, and the suction volume is relatively set. A variable volume mechanism that inhibits working fluid from returning from the working chamber to the suction path through the return path when it should be increased;
An inverter for driving the motor;
A control unit that controls the variable volume mechanism and the inverter so as to compensate for a decrease in the suction volume by an increase in the rotation speed of the motor;
A positive displacement compressor is provided.

  According to the present invention, by using the return path to return the working fluid from the working chamber to the suction path, the positive displacement compressor can be operated with a relatively small suction volume. On the other hand, if the working fluid is prohibited from returning from the working chamber to the suction path, the positive displacement compressor can be operated with a relatively large suction volume, that is, a normal suction volume. Furthermore, according to the present invention, the variable volume mechanism and the inverter are controlled so as to compensate for the decrease in the suction volume by the increase in the rotation speed of the motor. That is, instead of driving the motor at a low rotational speed, the suction volume is reduced. Therefore, it is possible to provide a positive displacement compressor that can exhibit high efficiency even when the load is small.

The longitudinal cross-sectional view of the rotary compressor which concerns on 1st Embodiment of this invention. Cross section taken along line II-II of the rotary compressor shown in FIG. Operational principle diagram of the rotary compressor shown in FIG. Graph showing the relationship between the rotation angle of the shaft and the volume of the suction chamber Graph showing the relationship between shaft rotation angle and compression-discharge chamber volume Control flow chart of variable displacement mechanism (open / close valve) and inverter Another control flow chart of variable displacement mechanism (open / close valve) and inverter A graph showing the relationship between the capacity of the rotary compressor, the suction volume of the compression mechanism, the state of the on-off valve, and the rotational speed of the motor Graph showing the relationship between rotary compressor capacity and rotary compressor efficiency Graph showing the relationship between the rotation angle of the shaft and the flow velocity of the refrigerant in the suction path Graph showing the relationship between the rotation angle of the shaft and the flow velocity of the refrigerant in the return path Graph showing the relationship between the rotation angle of the shaft and the flow rate of the refrigerant in the inlet pipe of the accumulator Vertical sectional view of a rotary compressor according to the second embodiment Cross section along line X-X of the rotary compressor shown in FIG. Cross-sectional view showing a modification of the connection position between the return path and the first working chamber Vertical sectional view of a rotary compressor according to the third embodiment Vertical sectional view of a rotary compressor according to the fourth embodiment Vertical sectional view of a rotary compressor according to the fifth embodiment Partial expanded sectional view in the low volume mode of the rotary compressor shown in FIG. Partial expanded sectional view in the high volume mode of the rotary compressor shown in FIG. Vertical sectional view of a scroll compressor according to a sixth embodiment Vertical sectional view of a scroll compressor according to a seventh embodiment Configuration diagram of a refrigeration cycle apparatus using the rotary compressor of the present embodiment Configuration diagram of conventional air conditioner

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited by the following embodiment. The type of the positive displacement compressor is not particularly limited. Examples of the positive displacement compressor include a rotary compressor, a scroll compressor, a reciprocating compressor, a screw compressor, and a swash plate compressor. In this specification, embodiments of a rotary compressor and a scroll compressor are described.

(First embodiment)
As shown in FIG. 1, the rotary compressor 100 of this embodiment includes a compressor body 40, an accumulator 12, a discharge path 11, a suction path 14, a return path 16, a variable volume mechanism 30, an inverter 42, and a control unit 44. ing.

  The compressor main body 40 includes a sealed container 1, a motor 2, a rotary compression mechanism 3, and a shaft 4. The compression mechanism 3 is disposed below the sealed container 1. The motor 2 is disposed above the compression mechanism 3 in the sealed container 1. The compression mechanism 3 and the motor 2 are connected by the shaft 4. A terminal 21 for supplying electric power to the motor 2 is provided on the top of the sealed container 1. An oil reservoir 22 for holding lubricating oil is formed at the bottom of the sealed container 1. The compressor body 40 has a so-called hermetic compressor structure.

  The discharge path 11, the suction path 14, and the return path 16 are each composed of a refrigerant pipe. The discharge path 11 penetrates the upper part of the sealed container 1 and is open inside the sealed container 1. The discharge path 11 plays a role of guiding a compressed working fluid (typically a refrigerant) to the 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, and penetrates the trunk of the sealed container 1. The suction path 14 plays a role of guiding the refrigerant to be compressed from the accumulator 12 to the working chamber 25 of the compression mechanism 3. The return path 16 has one end connected to the compression mechanism 3 at a position different from the suction path 14 and the other end connected to the accumulator 12, and penetrates the trunk of the sealed container 1. The return path 16 plays a role of returning the refrigerant once sucked into the working chamber 25 of the compression mechanism 3 to the suction path 14 before compression.

  The compression mechanism 3 is a positive displacement fluid mechanism and is moved by the motor 2 so as to compress the refrigerant. As shown in FIGS. 1 and 2, the compression mechanism 3 includes a cylinder 5, a piston 8, a vane 9, a spring 10, an upper bearing 6, and a lower bearing 7. Inside the cylinder 5, a piston 8 fitted to the eccentric portion 4 a of the shaft 4 is disposed so that a working chamber 25 is formed between the outer peripheral surface of the cylinder 5 and the inner peripheral surface of the cylinder 5. A vane groove 24 is formed in the cylinder 5. The vane groove 24 accommodates a vane 9 having a tip that contacts the outer peripheral surface of the piston 8. The spring 10 is disposed in the vane groove 24 so as to push the vane 9 toward the piston 8. The upper bearing 6 and the lower bearing 7 are respectively provided on the upper side and the lower side of the cylinder 5 so as to close the cylinder 5. The working chamber 25 between the cylinder 5 and the piston 8 is partitioned by the vane 9, thereby forming a suction chamber 25a and a compression-discharge chamber 25b. The refrigerant to be compressed is guided to the working chamber 25 (suction chamber 25a) through the suction path 14 and the suction port 27. A discharge port 29 is formed in the upper bearing 6 so that the compressed refrigerant is guided from the working chamber 25 (compression-discharge chamber 25b) to the internal space 28 of the sealed container 1. The discharge port 29 is provided with a discharge valve (not shown). The vane 9 may be integrated with the piston 8. That is, the piston 8 and the vane 9 may be configured as a so-called swing piston.

  The motor 2 includes a stator 17 and a rotor 18. The stator 17 is fixed to the inner peripheral surface of the sealed container 1. The rotor 18 is fixed to the shaft 4 and rotates together with the shaft 4. The piston 8 is moved inside the cylinder 5 by the motor 2. As the motor 2, a motor capable of changing the rotational speed, such as IPMSM (Interior Permanent Magnet Synchronous Mortar) and SPMSM (Surface Permanent Magnet Synchronous Mortar) can be used.

  The control unit 44 controls the inverter 42 to adjust the rotational speed of the motor 2, that is, the rotational speed of the rotary compressor 100. As the control unit 44, a DSP (Digital Signal Processor) including an A / D conversion circuit, an input / output circuit, an arithmetic circuit, a storage device, and the like can be used.

  The accumulator 12 includes a storage container 12a and an introduction pipe 12b. The storage container 12a has an internal space that can hold a liquid refrigerant and a gas refrigerant. The introduction pipe 12b passes through the upper part of the storage container 12a and opens toward the internal space of the storage container 12a. The suction path 14 and the return path 16 are connected to the accumulator 12 so as to penetrate the bottom of the storage container 12a. The suction path 14 and the return path 16 extend upward from the bottom of the storage container 12a and open toward the internal space of the storage container 12a at a certain height. That is, the return path 16 is connected to the suction path 14 via the internal space of the accumulator 12. It should be noted that another member such as a baffle may be provided inside the storage container 12a in order to reliably prevent the liquid refrigerant from proceeding directly from the introduction pipe 12b to the suction path 14.

  The variable volume mechanism 30 is provided in the return path 16. In the present embodiment, the variable volume mechanism 30 includes an on-off valve 32 and a check valve 35. That is, in this embodiment, the variable volume mechanism 30 does not have the ability to depressurize the refrigerant. Further, the refrigerant sucked into the suction chamber 25a is returned to the suction path 14 through the return path 16 without being substantially compressed in the compression-discharge chamber 25b. Therefore, the decrease in efficiency due to pressure loss is extremely small. However, as long as the efficiency of the rotary compressor 100 is not significantly affected, the variable volume mechanism 30 may have the ability to depressurize the refrigerant. For the same reason, the refrigerant compressed in the compression-discharge chamber 25 b may be returned to the suction path 14 through the return path 16.

  The on-off valve 32 is provided in the return path 16 outside the compressor body 40. On the other hand, the check valve 35 is provided inside the compressor body 40. As shown in FIGS. 1 and 2, the return path 16 communicates the upstream portion 16h formed inside the compression mechanism 3 (specifically, inside the cylinder 5), the working chamber 25, and the upstream portion 16h. And a return port 16p. The check valve 35 is provided in the upstream portion 16h. The check valve 35 prevents the refrigerant from flowing from the return path 16 to the working chamber 25. According to the check valve 35, the flow of the refrigerant from the return path 16 to the working chamber 25 can be prevented with a relatively simple structure without relying on electrical control.

  As shown in FIG. 2, the check valve 35 includes a valve body 36, a guide 37 and a spring 38. The valve body 36 is made of a thin metal plate having two surfaces, and is provided inside the guide 37 so as to reciprocate between a first position where the return port 16p is closed and a second position where the return port 16p is opened. Has been placed. One surface of the valve body 36 faces the return port 16p, and the other surface faces the spring 38. The spring 38 pushes the valve body 36 toward the return port 16p. A gap having an appropriate width is formed between the valve body 36 and the guide 37. When the valve body 36 moves away from the return port 16p, in other words, when the valve body 36 occupies the second position, the working chamber 25 communicates with the upstream portion 16h of the return path 16. When the valve body 36 contacts the return port 16p, in other words, when the valve body 36 occupies the first position, the working chamber 25 is isolated from the upstream portion 16h of the return path 16.

  The variable volume mechanism 30 plays a role of changing the suction volume (confinement volume) of the rotary compressor 100. When the suction volume of the rotary compressor 100 is to be relatively small, the refrigerant before compression is allowed to return from the working chamber 25 (specifically, the compression-discharge chamber 25b) to the suction passage 14 through the return passage 16. Specifically, the on-off valve 32 is opened. On the other hand, when the suction volume should be relatively increased, the refrigerant before compression is prohibited from returning from the working chamber 25 to the suction path 14 through the return path 16. Specifically, the on-off valve 32 is closed. When the on-off valve 32 is open, the rotary compressor 100 is operated in the low volume mode. When the on-off valve 32 is closed, the rotary compressor 100 is operated in the high volume mode.

  When the operation mode of the rotary compressor 100 is switched from the high volume mode to the low volume mode by controlling the variable volume mechanism 30, the inverter 42 is controlled so as to compensate for the decrease in the suction volume by the increase in the rotation speed of the motor 2. Is done. As a result, even when low capacity is required (when the load is small), the rotational speed of the motor 2 does not have to be extremely reduced. That is, the motor 2 can be driven at a rotational speed that can exhibit high efficiency even when low capacity is required. Therefore, the efficiency of the rotary compressor 100 is also improved.

  As shown in FIG. 2, the upstream portion 16 h and the return port 16 p of the return path 16 are formed at a position of 180 degrees with respect to the rotation angle of the shaft 4. In the present specification, the positions of the vane 9 and the vane groove 24 are defined as a “0 degree” reference position along the rotation direction of the shaft 4. In other words, the rotation angle of the shaft 4 at the moment when the vane 9 is pushed into the vane groove 24 by the piston 8 to the maximum is defined as “0 degree”.

In the high volume mode, the process of compressing the refrigerant confined in the compression-discharge chamber 25b (compression process) starts from a rotation angle of 0 degrees. On the other hand, in the low volume mode, the stroke of discharging the refrigerant confined in the compression-discharge chamber 25b from the return port 16p is performed in a period of 0 to 180 degrees, and the compression stroke starts from a rotation angle of 180 degrees. Therefore, when the suction volume in the high volume mode is V, the suction volume in the low volume mode is V / 2. Of course, the position of the return port 16p and the like can be appropriately changed according to the ratio of the suction volume to be changed. For example, when the return port 16p is formed at a position of 90 degrees, the suction volume in the low volume mode is {1+ (1/2) ^1/2 } V / 2.

  Next, the movement of the compression mechanism 3 will be described with reference to FIG.

  FIG. 3 shows how the shaft 4 and the piston 8 rotate counterclockwise. As the shaft 4 rotates, the volume of the suction chamber 25a increases. As shown in the upper left diagram of FIG. 3, when the shaft 4 makes one rotation, the volume of the suction chamber 25a is maximized. Thereafter, the suction chamber 25a changes to the compression-discharge chamber 25b. As the shaft 4 rotates, the volume of the compression-discharge chamber 25b decreases. As shown in FIGS. 4A and 4B, when the volume of the suction chamber 25a increases along points A, B, and C, the volume of the compression-discharge chamber 25b increases along points D, E, and F. Decrease.

  When the on-off valve 32 is open, as shown in the upper right view of FIG. 3, the check valve 35 opens as the volume of the compression-discharge chamber 25b decreases, and the refrigerant passes through the return port 16p and the compression-discharge chamber. It is discharged outside 25b. The discharged refrigerant is returned to the suction path 14 through the return path 16. Therefore, the pressure in the compression-discharge chamber 25b does not increase. As shown in the lower right diagram of FIG. 3, when the rotation angle of the shaft 4 reaches 180 degrees, the compression-discharge chamber 25b is isolated from the return path 16, and the refrigerant starts to be compressed in the compression-discharge chamber 25b. That is, the suction volume of the compression mechanism 3 is “V / 2”. The compression stroke continues until the pressure in the compression-discharge chamber 25b reaches the pressure in the internal space 28 of the sealed container 1. After the pressure in the compression-discharge chamber 25b reaches the pressure in the internal space 28, the discharge stroke is performed until the rotation angle of the shaft 4 reaches 360 degrees (0 degrees). As shown in the lower left diagram and the upper left diagram in FIG. 3, when the shaft 4 rotates once, the volume of the compression-discharge chamber 25 b becomes zero.

  When the on-off valve 32 is closed, the refrigerant cannot return from the working chamber 25 to the suction path 14 through the return path 16. Therefore, the suction volume of the compression mechanism 3 is “V”, and the compression stroke starts immediately after the suction stroke is completed. At this time, the portion of the return path 16 from the return port 16p to the on-off valve 32, that is, the upstream portion 16h of the return path 16 has a relatively high pressure. This is because when the on-off valve 32 is closed, the refrigerant compressed to the intermediate pressure is gradually accumulated in the upstream portion 16h. When the pressure in the compression-discharge chamber 25b is lower than the pressure in the upstream portion 16h, the check valve 35 prevents the refrigerant from flowing back from the feedback path 16 to the compression-discharge chamber 25b. That is, since the check valve 35 is provided on the working chamber 25 side when viewed from the on-off valve 32, the return path 16 can be prevented from becoming a dead volume. In this embodiment, since the check valve 35 is provided in the upstream portion 16h formed inside the cylinder 5, the dead volume due to the return path 16 is substantially zero.

  Next, the control procedure of the variable volume mechanism 30 (open / close valve 32) and the inverter 42 by the control unit 44 will be described with reference to FIG. 5A.

  In step S1, the number of rotations of the motor 2 is adjusted according to the requested capacity. Specifically, the rotation speed of the motor 2 is adjusted so that a necessary refrigerant flow rate is obtained. Next, in step S2 and step S6, it is determined whether the rotational speed of the motor 2 has been reduced or increased. If the process of reducing the rotational speed is being performed in step S1, the process proceeds to step S3 to determine whether the current rotational speed is 30 Hz or less. If the current rotational speed is 30 Hz or less, it is determined in step S4 whether the on-off valve 32 is closed. When the on-off valve 32 is closed, in step S5, a process of opening the on-off valve 32 and a process of increasing the rotational speed of the motor 2 to twice the current rotational speed are executed. The order of the processes in step S5 is not particularly limited, but the rotational speed of the motor 2 can be increased almost simultaneously with opening the on-off valve 32.

  On the other hand, when the process for increasing the rotational speed is performed in step S1, the process proceeds to step S7 to determine whether the current rotational speed is 70 Hz or higher. If the current rotational speed is 70 Hz or higher, it is determined in step S8 whether the on-off valve 32 is open. If the on-off valve 32 is open, a process of closing the on-off valve 32 and a process of reducing the rotational speed of the motor 2 to 1/2 the current rotational speed are executed in step S9. The order of the processes in step S9 is not particularly limited, but the rotational speed of the motor 2 can be reduced almost simultaneously with closing the on-off valve 32.

  By performing the control according to the flowchart of FIG. 5A, the relationship between the state of the on-off valve 32 and the rotation speed of the motor 2 has hysteresis as shown in FIG. According to such control, hunting of the compression mechanism 3 can be prevented.

  The suction volume of the compression mechanism 3 in the high volume mode in which the on-off valve 32 is closed, that is, the refrigerant is prohibited from returning from the working chamber 25 to the suction path 14 through the return path 16 is “V”. When the rotational speed of the motor 2 decreases from the high rotational speed to the first rotational speed (for example, 30 Hz) or less during operation in the high volume mode, the control unit 44 performs processing related to the opening / closing valve 32 and the motor for reducing the suction volume. 2 for increasing the number of revolutions of 2. The process related to the on-off valve 32 for reducing the suction volume is a process of opening the on-off valve 32. The process related to the inverter 42 for increasing the rotation speed of the motor 2 is a process of setting the target rotation speed of the motor 2 to twice the most recent rotation speed.

  Further, the control unit 44 controls the on-off valve 32 and the inverter 42 so as to compensate for the increase in the suction volume by the decrease in the rotation speed of the motor 2. The suction volume of the compression mechanism 3 in the low volume mode in which the on-off valve 32 is opened, that is, the refrigerant is allowed to return from the working chamber 25 to the suction path 14 through the return path 16 is “V / 2”. When the rotation speed of the motor 2 increases to a second rotation speed (for example, 70 Hz) or more during operation in the low volume mode, the control unit 44 performs processing related to the on-off valve 32 for increasing the suction volume and the rotation speed of the motor 2. And the process of the inverter 42 for lowering. The process related to the on-off valve 32 for increasing the suction volume is a process of closing the on-off valve 32. The process related to the inverter 42 for reducing the rotational speed of the motor 2 is a process of setting the target rotational speed of the motor 2 to ½ times the latest rotational speed.

  As shown in FIG. 6, when the rotational speed of the motor 2 is reduced to 30 Hz with the on-off valve 32 closed, the on-off valve 32 is opened and the rotational speed of the motor 2 is increased to 60 Hz. When the rotational speed of the motor 2 rises to 70 Hz with the open / close valve 32 open, the open / close valve 32 is closed and the rotational speed of the motor 2 is lowered to 35 Hz. When the opening / closing valve 32 is opened and the rotation speed of the motor 2 is increased, the rotation speed is the third rotation speed. When the opening / closing valve 32 is closed and the rotation speed of the motor 2 is decreased, the rotation speed is the fourth rotation speed. Then, the relationship of (first rotation speed) <(fourth rotation speed), (third rotation speed) <(second rotation speed) is established. For example, by setting the first rotational speed to a rotational speed of 30 Hz or less, the rotary compressor 100 can be operated with a wider range of capabilities. The lower limit of the first rotation speed is not particularly limited, but is 20 Hz, for example.

  When the operation mode is switched, the rotation speed of the motor 2 can be adjusted according to 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 switching from the high volume mode to the low volume mode, the rotation speed (target rotation speed) of the motor 2 is set to a rotation speed obtained by dividing the rotation speed of the motor 2 immediately before the mode switching by the ratio (VL / VH). . Similarly, when switching from the low volume mode to the high volume mode, the rotation speed of the motor 2 is set to a rotation speed obtained by multiplying the rotation speed of the motor 2 immediately before the mode switching by a ratio (VL / VH). In this way, the operation mode can be smoothly switched between the high volume mode and the low volume mode.

  It is not essential to compensate 100% for the decrease in the capacity of the rotary compressor 100 due to the decrease in the suction volume by the increase in the capacity of the rotary compressor 100 due to the increase in the rotation speed of the motor 2. In the example shown in FIG. 6, when the opening / closing valve 32 is opened and the suction volume is reduced to ½, the number of rotations of the motor 2 is doubled, so that the capacity of the rotary compressor 100 is changed by mode switching. Not. However, there is no particular problem even if the capacity of the rotary compressor 100 increases or decreases due to mode switching.

  In order to prevent the refrigerant from being trapped in the upstream portion 16h of the return path 16 while the rotary compressor 100 is stopped, the rotary compressor 100 may be stopped with the on-off valve 32 opened. As the on-off valve 32, a normally open valve can be used. The check valve 35 may be a known reed valve including a reed made of a thin metal plate and a stopper.

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

  Even if the rotational speed of the motor 2 is reduced to the first rotational speed (for example, 30 Hz) in the high volume mode, the process related to the on-off valve 32 for reducing the suction volume and the rotational speed of the motor 2 when the refrigerant flow rate is excessive. The control unit 44 may be configured to execute processing related to the inverter 42 for increasing the power. That is, the control unit 44 may be configured to determine whether or not mode switching is necessary before actually reducing the rotational speed of the motor 2 to the first rotational speed. Similarly, if the flow rate of the refrigerant is insufficient even if the number of rotations of the motor 2 is increased to the second number of rotations (for example, 70 Hz) in the low volume mode, the processing related to the opening / closing valve 32 for increasing the suction volume and the motor 2 The control unit 44 may be configured to execute processing related to the inverter 42 for reducing the rotational speed. That is, the controller 44 may be configured to determine whether or not mode switching is necessary before actually increasing the rotation speed of the motor 2 to the second rotation speed. An example of such control will be described with reference to FIG. 5B.

  As shown in FIG. 5B, first, the required number of rotations of the motor 2 is calculated in step S11. “Necessary rotational speed” means, for example, the rotational speed for obtaining a necessary refrigerant flow rate. Next, in step S12, it is determined whether the necessary rotation speed is equal to or lower than the first rotation speed (for example, 30 Hz). If the necessary rotation speed is equal to or lower than the first rotation speed, it is determined in step S13 whether the on-off valve 32 is closed. When the on-off valve 32 is closed, in step S15, the on-off valve 32 is opened, and the rotation speed of the motor 2 is adjusted to a rotation speed at which a necessary refrigerant flow rate can be obtained. If the on-off valve 32 is open, only the rotation speed of the motor 2 is adjusted in step S14.

  On the other hand, if the required rotational speed is greater than the first rotational speed, it is determined in step S16 whether the required rotational speed is greater than or equal to the second rotational speed (for example, 70 Hz). If the required rotation speed is equal to or higher than the second rotation speed, it is determined in step S17 whether the on-off valve 32 is open. If the on-off valve 32 is open, in step S18, the on-off valve 32 is closed and the rotational speed of the motor 2 is adjusted to a rotational speed at which a necessary refrigerant flow rate can be obtained. If the on-off valve 32 is closed, only the rotation speed of the motor 2 is adjusted in step S19.

  By performing the control described with reference to FIG. 5A or 5B, the rotary compressor 100 exhibits high efficiency even when low capacity is required (when the load is small), as shown by the solid line in FIG. Yes. In FIG. 7, the rated capacity of the rotary compressor 100 is “100%”. The efficiency of the rotary compressor 100 decreases with a decrease in the capacity to be exhibited, that is, with a decrease in the rotational speed of the motor 2, based on the rated capacity. As indicated by the broken line, when the motor 2 is driven at a rotational speed equal to or less than 50% of the rated rotational speed, the reduction in efficiency becomes significant. In this embodiment, when a relatively low capacity is required, the operation is performed in the low volume mode with the suction volume V / 2. Thereby, the motor 2 can be driven at a rotational speed as close to the rated rotational speed as possible. Therefore, the rotary compressor 100 can exhibit excellent efficiency even when the required capacity is 50% or less of the rated capacity.

  Next, an effect based on the fact that the return path 16 communicates with the suction path 14 through the internal space of the accumulator 12 will be described.

  All the refrigerant present in the suction path 14 is basically sucked into the suction chamber 25a. Therefore, as shown in FIG. 8A, the flow rate of the refrigerant in the suction path 14 changes in proportion to the rate of change of the volume of the suction chamber 25a (see FIG. 4A). Specifically, the flow rate of the refrigerant in the suction path 14 theoretically shows a sinusoidal profile with respect to the rotation angle of the shaft 4.

  When the on-off valve 32 is open, the refrigerant in the compression-discharge chamber 25b is discharged to the return path 16 through the return port 16p during a period in which the rotation angle of the shaft 4 is 0 to 180 degrees. The amount of refrigerant discharged from the compression-discharge chamber 25b to the return path 16 is equal to the amount of decrease in the volume of the compression-discharge chamber 25b during the period of 0 to 180 degrees. As shown in FIG. 8B, the flow rate of the refrigerant in the return path 16 is proportional to the rate of change of the volume of the compression-discharge chamber 25b (see FIG. 4B) only during the period in which the rotation angle of the shaft 4 is 0 to 180 degrees. Change. Specifically, the flow velocity of the refrigerant in the return path 16 theoretically shows a sinusoidal profile in a period of 0 to 180 degrees and becomes zero in a period of 180 to 360 degrees.

  The refrigerant flows into the accumulator 12 from both the introduction pipe 12 b and the return path 16. The refrigerant flowing into the accumulator 12 can only travel to the suction path 14. Therefore, the flow rate of the refrigerant in the introduction pipe 12b of the accumulator 12 substantially matches the difference between the flow rate of the refrigerant in the suction path 14 and the flow rate of the refrigerant in the return path 16. Specifically, as shown in FIG. 8C, the flow rate of the refrigerant in the introduction pipe 12b theoretically shows a sinusoidal profile in the period of 180 to 360 degrees and becomes zero in the period of 0 to 180 degrees. .

  When the rotation angle of the shaft 4 is 180 degrees, the refrigerant flow in the return path 16 rapidly decreases from the maximum flow velocity v to zero. When the rotation angle of the shaft 4 is 180 degrees, the refrigerant flow in the introduction pipe 12b increases rapidly from zero to the maximum flow velocity v. Such a rapid change in the flow velocity promotes the occurrence of water hammer, and may cause problems such as a decrease in reliability due to vibration of the pipes constituting the suction path 14 and the return path 16 and generation of noise. . Furthermore, the pressure wave transmitted to the suction path 14 may reduce the volumetric efficiency of the suction chamber 25a, which may reduce the efficiency of the rotary compressor 100. However, in this embodiment, the return path 16 is connected to the suction path 14 via the internal space of the accumulator 12. According to this configuration, since the occurrence of water hammer can be prevented, the reduction of vibration, noise and efficiency can be effectively suppressed.

(Second Embodiment)
As shown in FIG. 9, the rotary compressor 200 of the present embodiment includes a second compression mechanism 33 in addition to the compression mechanism 3 described in the first embodiment. Hereinafter, the elements of the compression mechanism 3 described in the first embodiment are marked with “first”. For example, the cylinder 5 is denoted as the first cylinder 5, the piston 8 as the first piston 8, the vane 9 as the first vane 9, the working chamber 25 as the first working chamber 25, and the compression mechanism 3 as the first compression mechanism 3. In the following, the same components as those described above are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIGS. 9 and 10, the second compression mechanism 33 includes a second cylinder 55, a second piston 58, a second vane 59, and a second spring 60. The second cylinder 55 is arranged concentrically with the first cylinder 5. The second cylinder 55 is fitted into the second eccentric portion 4b of the shaft 4 so that a second working chamber 75 is formed between the outer peripheral surface of the second cylinder 55 and the inner peripheral surface of the second cylinder 55. A second piston 58 is arranged. A second vane groove 64 is formed in the second cylinder 55. The second vane groove 64 houses a second vane 59 having a tip that contacts the outer peripheral surface of the second piston 58. The second spring 60 is disposed in the second vane groove 64 so as to push the second vane 59 toward the second piston 58. The second working chamber 75 between the second cylinder 55 and the second piston 58 is partitioned by a second vane 59, thereby forming a second suction chamber 75a and a second compression-discharge chamber 75b. The refrigerant to be compressed is guided to the second working chamber 75 (second suction chamber 75a) through the second suction path 15 and the second suction port 77. A second discharge port 79 is formed in the upper bearing 6 so that the compressed refrigerant is guided from the second working chamber 75 (second compression-discharge chamber 75b) to the internal space 28 of the sealed container 1. The second discharge port 79 is provided with a discharge valve (not shown).

  The lower bearing 7 is covered with a muffler 23 having an internal space that can receive the refrigerant compressed by the first compression mechanism 3. The first discharge port 29 of the first compression mechanism 3 is formed in the lower bearing 7. The lower bearing 7, the first cylinder 5, the middle plate 53, the second cylinder 55, and the upper cylinder are moved so that the refrigerant compressed by the first compression mechanism 3 moves from the inner space of the muffler 23 to the inner space 28 of the sealed container 1. A flow path 26 penetrating the bearing 6 is formed.

  The protruding direction of the first eccentric portion 4a is shifted by 180 degrees from the protruding direction of the second eccentric portion 4b. That is, the phase of the first piston 8 is shifted by 180 degrees between the phase of the second piston 58 and the rotation angle of the shaft 4.

  A refrigerant is supplied to the first compression mechanism 3 through the first suction path 14. The refrigerant is supplied to the second compression mechanism 33 through the second suction path 15. The refrigerant is compressed by the first compression mechanism 3 or the second compression mechanism 33 and discharged into the internal space 28 of the sealed container 1. The first suction path 14 and the second suction path 15 are each connected to the accumulator 12. Note that one of the suction paths 14 and 15 may be branched from the other inside or outside the accumulator 12.

  As shown in FIGS. 9 and 10, since the feedback path 16 is not connected to the second compression mechanism 33, the suction volume of the second compression mechanism 33 is always constant. The return path 16 is connected only to the first compression mechanism 3 so that only the suction volume of the first compression mechanism 3 can be changed. By allowing only the suction volume of the first compression mechanism 3 to be changed, the production cost of the rotary compressor 200 can be suppressed. Of course, the return path 16 may be connected to each of the compression mechanisms 3 and 33 so that the suction volumes of the compression mechanisms 3 and 33 can be changed.

  In the present embodiment, the first compression mechanism 3 is disposed on the side far from the motor 2, and the second compression mechanism 33 is disposed on the 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 the axial direction of the shaft 4. Since the second compression mechanism 33 has a constant suction volume, a large load torque is required even in the low volume mode. Therefore, when the second compression mechanism 33 is disposed on the side closer to the motor 2, the load applied to the shaft 4 in the low volume mode is reduced, and thereby the loss in the bearings 6 and 7 can be reduced. Further, when the first compression mechanism 3 having a small suction volume in the low volume mode is disposed on the lower side, the pressure loss caused by the compressed refrigerant flowing into the internal space 28 of the sealed container 1 through the muffler 23. Can be reduced. However, the positional relationship between the first compression mechanism 3 and the second compression mechanism 33 is not limited to the above relationship.

  As described in the first embodiment, when the return port 16p is formed at a position of 180 degrees, “V” or “V / 2” can be selected as the suction volume of the first compression mechanism 3. Furthermore, when the suction volume of the second compression mechanism 33 is “V”, “2 V” or “1.5 V” can be selected as the sum of the suction volumes of the compression mechanisms 3 and 33.

  On the other hand, in the low volume mode in which the refrigerant is allowed to return from the first working chamber 25 to the first suction path 14 through the return path 16, the suction volume of the first compression mechanism 3 can be made substantially zero. Specifically, as shown in FIG. 11, the return port 16 p may be formed at a position close to the first discharge port 29. According to this configuration, in the low volume mode, substantially all of the refrigerant sucked into the first suction chamber 25a is returned to the accumulator 12 through the return path 16 without being compressed. That is, the function of the first compression mechanism 3 can be canceled. The total suction volume of the compression mechanisms 3 and 33 in the low volume mode is equal to the suction volume V of the second compression mechanism 33.

Note that “making the suction volume of the first compression mechanism 3 substantially zero” does not necessarily mean that the suction volume of the first compression mechanism 3 is completely zero. For example, when the suction volume in the high volume mode is V, the suction volume in the low volume mode is less than {1- (1/2) ^1/2 } V / 2, preferably less than V / 10. The position of the return port 16p can be determined. According to this configuration, it can be said that the first compression mechanism 3 does not perform compression work on the refrigerant in the low volume mode, and the function is lost.

(Third embodiment)
As shown in FIG. 12, the rotary compressor 300 of the present embodiment is obtained by omitting the check valve 35 from the rotary compressor 100 of the first embodiment. In the first and second embodiments, the variable volume mechanism 30 includes an on-off valve 32 and a check valve 35. The check valve 35 contributes to the reduction of the dead volume, but is not directly involved in the change of the suction volume. Therefore, even if the variable volume mechanism 30 is configured only by the on-off valve 32 as in the present embodiment, the suction volume of the compression mechanism 3 can be changed.

(Fourth embodiment)
As shown in FIG. 13, the rotary compressor 400 of the present embodiment includes a valve 80 (electromagnetic valve 80) that can directly open and close the feedback port 16 p as the variable volume mechanism 30. Other configurations are as described in the first embodiment.

  The electromagnetic valve 80 includes a plunger 81, a coil 83, and a housing 85. The housing 85 has an internal flow path 85 h as an upstream portion of the return path 16 and a return port 16 p that opens toward the working chamber 25. The plunger 81 is accommodated in the housing 85 so as to advance and retract along the internal flow path 85h. When the coil 83 is energized, the plunger 81 moves away from the shaft 4 and the return port 16p is opened. Thereby, the refrigerant can return from the working chamber 25 to the suction path 14 through the return path 16. When energization of the coil 83 is stopped, the plunger 81 is pushed out in the direction approaching the shaft 4, and the return port 16 p is closed at the tip of the plunger 81.

  In the low volume mode, the coil 83 is energized to open the return port 16p. In the high volume mode, energization of the coil 83 is stopped and the return port 16p is closed. Since the return port 16p is directly opened and closed by the plunger 81, the dead volume when the return port 16p is closed is substantially zero. That is, according to the electromagnetic valve 80 of the present embodiment, not only switching between the high volume mode and the low volume mode but also preventing the intermediate-pressure refrigerant from flowing back and re-expanding into the suction chamber 25a in the high volume mode can be prevented. Further, according to the present embodiment, since the return port 16p is always open in the low volume mode, the refrigerant to be compressed can be supplied from both the suction port 27 and the return port 16p to the suction chamber 25a. This is preferable from the viewpoint of reducing the pressure loss in the suction stroke. This effect is also obtained in the third and fifth embodiments.

  Further, the solenoid 83 may be controlled so that the feedback port 16p opens and closes in synchronization with the rotation of the shaft 4. That is, by adjusting the opening / closing timing of the return port 16p, the suction volume of the compression mechanism 3 can be changed in multiple stages or continuously. For example, the coil 83 is energized so that the refrigerant can flow into the return path 16 during a period in which the rotation angle of the shaft 4 is 0 to 90 degrees. During the period in which the rotation angle of the shaft 4 is 90 to 360 degrees, the energization to the coil 83 is stopped. In this way, the rotary compressor 400 can be operated in the medium volume mode in addition to the high volume mode and the low volume mode described above.

(Fifth embodiment)
As shown in FIG. 14, the rotary compressor 500 of this embodiment has a variable volume mechanism 30 having a structure different from that of the rotary compressor 100 of the first embodiment. Other configurations are as described in the first embodiment.

  The rotary compressor 500 includes a three-way valve 90, a volume control valve 91, and a high-pressure path 92 as the variable volume mechanism 30. The return path 16 has an upstream portion 16 h formed inside the compression mechanism 3 (specifically, inside the cylinder 5) and a return port 16 p that opens toward the working chamber 25. A volume control valve 91 is disposed in the upstream portion 16h so that the return port 16p can be opened and closed. The high pressure path 92 has one end connected to the three-way valve 90 and the other end connected to the oil reservoir 22. The high-pressure path 92 is a path for supplying the volume control valve 91 with a pressure equal to the pressure of the compressed refrigerant. The rotary compressor 500 of the present embodiment is a so-called high pressure shell type compressor in which the internal space 28 of the sealed container 1 is filled with a compressed refrigerant. The oil reservoir 22 holds oil having a pressure substantially equal to the pressure of the compressed refrigerant. The three-way valve 90 is configured to connect either the suction path 14 or the high-pressure path 92 to the upstream portion 16 h of the return path 16. By controlling the three-way valve 90, the rotary compressor 500 can be operated in either the high volume mode or the low volume mode.

  As shown in FIGS. 15A and 15B, the volume control valve 91 includes a plunger 96 and a spring 97. The plunger 96 has a cylindrical shape having a bottom surface facing the return port 16p, and is arranged so as to be slidable into the cylindrical upstream portion 16h. The spring 97 is coupled to the inside of the plunger 96, and applies a force in a direction away from the return port 16p to the plunger 96. A groove 16 g is formed along the outer peripheral surface of the plunger 96 in the upstream portion 16 h of the return path 16. The groove 16g extends along the sliding direction of the plunger 96 and has a dimension longer than the length of the plunger 96 in the sliding direction.

  As shown in FIG. 15A, in the low volume mode, the three-way valve 90 is controlled so that the suction path 14 communicates with the upstream portion 16 h of the return path 16. Then, the plunger 96 is separated from the return port 16p, and the refrigerant can flow from the working chamber 25 to the return path 16 through the return port 16p and the groove 16g. That is, when the suction path 14 is connected to the upstream portion 16 h of the return path 16 by the three-way valve 90, the volume control valve 91 is opened to allow the refrigerant to flow from the working chamber 25 to the suction path 14.

  On the other hand, as shown in FIG. 15B, in the high volume mode, the three-way valve 90 is controlled so that the high-pressure path 92 communicates with the upstream portion 16h of the return path 16. Then, the pressure of the oil in the oil reservoir 22 acts on the back surface of the plunger 96, the plunger 96 is pressed against the return port 16 p with a force larger than the force of the spring 97, and the refrigerant flows from the working chamber 25 to the return path 16. It becomes a state that can not be. That is, when the high-pressure path 92 is connected to the upstream portion 16 h of the return path 16 by the three-way valve 90, the volume control valve 91 is closed and the refrigerant flow from the working chamber 25 to the suction path 14 is prohibited.

  As described in the first embodiment, when the check valve 35 is employed, the check valve 35 opens and closes in synchronization with the rotation of the shaft 4. On the other hand, the volume control valve 91 employed in the present embodiment is always open or always closed. Therefore, it is advantageous for reducing vibration, noise and pressure loss. Also in this embodiment, since the volume control valve 91 is configured to directly open and close the feedback port 16p, the problem of dead volume can be solved.

  In the present embodiment, the high-pressure path 92 has one end connected (opened) to the oil reservoir 22. In order to achieve the purpose of supplying high pressure to the volume control valve 91, one end of the high pressure path 92 may be connected to any part of the internal space 28 of the sealed container 1. Further, when the rotary compressor 500 is used in a refrigeration cycle apparatus, the high pressure path 92 may be connected to a high pressure portion of the refrigerant circuit (for example, a portion between the rotary compressor 500 and the radiator). However, according to the present embodiment, when the volume control valve 91 is closed by applying a high pressure to the plunger 96, an oil sealing effect can be obtained. This is preferable from the viewpoint of preventing a decrease in efficiency due to refrigerant leakage. According to the present embodiment, it is possible to prevent liquid refrigerant from accumulating in the upstream portion 16h of the return path 16 and insufficient refrigerant amount. Even if the upstream portion 16h of the return path 16 is filled with oil, the volume change of the oil with respect to the temperature change is small. Therefore, even if the rotary compressor 500 is stopped in a state where the oil is confined in the upstream portion 16h of the return path 16, no malfunction occurs. Of course, the rotary compressor 500 may be stopped in a state where the suction path 14 communicates with the upstream portion 16 h of the return path 16.

(Sixth embodiment)
As shown in FIG. 16, the scroll compressor 600 of this embodiment includes a scroll compression mechanism 603. The compression mechanism 603 includes an orbiting scroll 607, a fixed scroll 608, an Oldham ring 611, a bearing member 610, and a muffler 616. The orbiting scroll 607 and the fixed scroll 608 have spiral wraps 627 and 628, respectively. A crescent-shaped working chamber 612 is formed between the wrap 627 and the wrap 628. The orbiting scroll 607 is fitted to the eccentric shaft 4 a of the shaft 4, and its rotation motion is prohibited by the Oldham ring 611. A discharge port 638 is formed at the center of the fixed scroll 608. A passage 617 is formed in the fixed scroll 608 and the bearing member 610 so as to penetrate therethrough.

  When the shaft 4 rotates, the orbiting scroll 607 performs an orbiting motion while the wrap 627 is engaged with the wrap 628. The working chamber 612 reduces its volume while moving from the outside to the inside. As a result, the refrigerant sucked from the suction passage 14 is compressed. The compressed refrigerant is discharged to the internal space 28 of the sealed container 1 through the discharge port 638, the internal space 619 of the muffler 616, and the flow path 617 in this order. Thereafter, the refrigerant discharged into the internal space 28 is guided to the outside of the compressor 600 through the discharge path 11.

  The scroll compressor 600 has the variable volume mechanism 30 described in the first embodiment. In the present embodiment, the upstream portion 16 h of the return path 16 is formed inside the compression mechanism 603, specifically, inside the fixed scroll 608. The fixed scroll 608 is also provided with a return port 16p so that the working chamber 612 can communicate with the return path 16. The check valve 35 is attached to the fixed scroll 608 so that the return port 16p can be opened and closed. Similar to the rotary compressor 100, the ratio of the suction volume in the low volume mode to the suction volume in the high volume mode changes according to the position of the return port 16p.

  The configuration and operation of the variable volume mechanism 30 are as described in the first embodiment. The control when switching between the high volume mode and the low volume mode is also as described in the first embodiment. Therefore, according to the scroll compressor 600, the same effect as the rotary compressor 100 is acquired. In this embodiment, no accumulator is provided, and the return path 16 is directly connected to the suction path 14 near the compression mechanism 603. However, an accumulator may be provided as in some previous embodiments.

(Seventh embodiment)
As shown in FIG. 17, the scroll compressor 700 of this embodiment includes the variable volume mechanism 30 including the three-way valve 90, the volume control valve 91, and the high pressure path 92, that is, the variable volume mechanism 30 described in the fifth embodiment. Have. As described in the sixth embodiment, the upstream portion 16 h and the return port 16 p of the return path 16 are formed in the fixed scroll 608. The volume control valve 91 is attached to the fixed scroll 608 so that the return port 16p can be opened and closed. In the scroll compressor 700, the configuration and operation of the variable volume mechanism 30 are as described in the fifth embodiment. The control when switching between the high volume mode and the low volume mode is also as described in the fifth embodiment. Therefore, according to the scroll compressor 700, the same effect as the rotary compressor 500 is acquired.

  In addition, the configuration described with reference to FIGS. 12 and 13 can be applied to the scroll compressor.

(Application embodiment)
As shown in FIG. 18, a refrigeration cycle apparatus 800 can be constructed using a rotary compressor 100. The refrigeration cycle apparatus 800 includes a rotary compressor 100, a radiator 802, an expansion mechanism 804, and an evaporator 806. These devices are connected in the above order by refrigerant pipes so as to form a refrigerant circuit. The radiator 802 is configured by, for example, an air-refrigerant heat exchanger, and cools the refrigerant compressed by the rotary compressor 100. The expansion mechanism 804 is composed of an expansion valve, for example, and expands the refrigerant cooled by the radiator 802. The evaporator 806 is composed of, for example, an air-refrigerant heat exchanger, and heats the refrigerant expanded by the expansion mechanism 804. Instead of the rotary compressor 100 of the first embodiment, the compressors 200, 300, 400, 500, 600, or 700 of the second to fifth embodiments may be used.

(Other)
The several embodiments described in this specification can be combined with each other without departing from the scope of the invention. For example, even if the check valve 35 described in the first embodiment is combined with the three-way valve 90 described in the fifth embodiment, the effects described in the first embodiment can be obtained.

  In addition, when the rotary compressor 100 is started, the variable volume mechanism 30 can be controlled so as to allow the refrigerant to return from the working chamber 25 to the suction path 14 through the return path 16. That is, the rotary compressor 100 is temporarily operated in the low volume mode at the time of startup.

INDUSTRIAL APPLICATION This invention is useful for the compressor of the refrigerating-cycle apparatus which can be utilized for a water heater, a warm water heating apparatus, an air conditioning apparatus etc. The present invention is particularly useful for a compressor of an air conditioner that requires a wide range of capabilities.

Claims (14)

A compression mechanism having a working chamber;
A motor for moving the compression mechanism;
A suction path for leading the working fluid to be compressed to the working chamber;
A return path for returning the working fluid from the working chamber to the suction path;
When the suction volume of the compression mechanism, which is provided in the return path, should be relatively small, the working fluid is allowed to return from the working chamber to the suction path through the return path, and the suction volume is relatively set. A variable volume mechanism that inhibits working fluid from returning from the working chamber to the suction path through the return path when it should be increased;
An inverter for driving the motor;
A control unit that controls the variable volume mechanism and the inverter so as to compensate for a decrease in the suction volume by an increase in the rotation speed of the motor;
A positive displacement compressor.   When the rotational speed of the motor drops below the first rotational speed during operation in the high volume mode in which the working fluid is prohibited from returning from the working chamber to the suction path through the return path, or in the high volume mode Even when the rotational speed of the motor is reduced to the first rotational speed, when the flow rate of the working fluid is excessive, the control unit performs processing related to the variable volume mechanism for reducing the suction volume and rotation of the motor. The positive displacement compressor according to claim 1, wherein the processing related to the inverter for increasing the number is executed.   The positive displacement compressor according to claim 1, wherein the control unit controls the variable volume mechanism and the inverter so as to compensate for an increase in the suction volume by a decrease in the rotation speed of the motor.   When the rotational speed of the motor rises above the second rotational speed during operation in the low volume mode that allows the working fluid to return from the working chamber to the suction path through the return path, or in the low volume mode Even when the rotational speed of the motor is increased to the second rotational speed, when the flow rate of the working fluid is insufficient, the control unit performs processing related to the variable volume mechanism for increasing the suction volume and the rotational speed of the motor. The positive displacement compressor according to claim 3, wherein a process related to the inverter for lowering is performed. When the rotational speed of the motor drops below the first rotational speed during operation in the high volume mode in which the working fluid is prohibited from returning from the working chamber to the suction path through the return path, or in the high volume mode Even when the rotational speed of the motor is reduced to the first rotational speed, when the flow rate of the working fluid is excessive, the control unit performs processing related to the variable volume mechanism for reducing the suction volume and rotation of the motor. Processing for the inverter to increase the number,
When the rotational speed of the motor rises above the second rotational speed during operation in the low volume mode that allows the working fluid to return from the working chamber to the suction path through the return path, or in the low volume mode Even when the rotational speed of the motor is increased to the second rotational speed, when the flow rate of the working fluid is insufficient, the control unit performs processing related to the variable volume mechanism for increasing the suction volume and the rotational speed of the motor. The positive displacement compressor according to claim 3, wherein a process related to the inverter for lowering is performed.   The positive displacement compressor according to claim 2 or 5, wherein the first rotational speed is set to a rotational speed of 30 Hz or less. An accumulator having an internal space capable of holding a working fluid and connected to the suction path and the return path;
The positive displacement compressor according to any one of claims 1 to 6, wherein the return path is connected to the suction path via the internal space of the accumulator.   The control unit controls the variable volume mechanism to allow the working fluid to return from the working chamber to the suction path through the return path when the positive displacement compressor is started. The positive displacement compressor according to any one of 7.   The positive displacement compressor according to any one of claims 1 to 8, wherein the variable displacement mechanism includes an on-off valve provided in the return path. The return path includes an upstream portion formed within the compression mechanism;
The variable volume mechanism further includes a check valve provided in the upstream portion,
The positive displacement compressor according to claim 9, wherein a flow of the working fluid from the return path to the working chamber is blocked by the check valve. The return path includes an upstream portion formed within the compression mechanism;
The variable volume mechanism includes a three-way valve, a volume control valve provided in the upstream portion, and a high-pressure path for supplying a pressure equal to the pressure of the compressed working fluid to the volume control valve;
The positive displacement compressor according to any one of claims 1 to 8, wherein the three-way valve is configured to connect either the suction path or the high-pressure path to the upstream portion of the return path. . The volume control valve includes a plunger and a spring;
When the high-pressure path is connected to the upstream portion of the return path by the three-way valve, the volume control valve is closed and the flow of working fluid from the working chamber to the suction path is prohibited,
12. The volume control valve opens to allow the flow of working fluid from the working chamber to the suction path when the suction path is connected to the upstream portion of the return path by the three-way valve. The positive displacement compressor described in 1. The compression mechanism includes a cylinder, a piston disposed inside the cylinder such that the working chamber is formed between an outer peripheral surface of the cylinder and an inner peripheral surface of the cylinder, and the working chamber as a suction chamber. A rotary compression mechanism having a vane partitioning into a compression-discharge chamber;
When the cylinder is defined as a first cylinder, the piston as a first piston, the vane as a first vane, the working chamber as a first working chamber, and the compression mechanism as a first compression mechanism,
The positive displacement compressor further includes a second compression mechanism having a second cylinder, a second piston, and a second vane, and the second piston being moved by the motor common to the first compression mechanism,
The suction volume of the second compression mechanism is constant;
The positive displacement compressor according to any one of claims 1 to 12, wherein the return path is connected only to the first compression mechanism so that only the suction volume of the first compression mechanism can be changed.   The suction volume of the first compression mechanism is substantially zero in a low volume mode that allows working fluid to return from the first working chamber to the suction path through the return path. Positive displacement compressor.

Images