WO2018003015A1

WO2018003015A1 - Single screw compressor and refrigeration cycle device

Info

Publication number: WO2018003015A1
Application number: PCT/JP2016/069131
Authority: WO
Inventors: 栗田　慎
Original assignee: 三菱電機株式会社
Priority date: 2016-06-28
Filing date: 2016-06-28
Publication date: 2018-01-04
Also published as: TWI639770B; TW201800668A

Abstract

This single screw compressor is configured such that: the inside of a casing is divided into a first space, into which fluid flows from the outside, and a second space, in which a compression chamber is located; and the compression chamber and a suction port which provides communication between the first space and the second space are located at a higher position than the axis of a rotating shaft.

Description

Single screw compressor and refrigeration cycle equipment

The present invention relates to a technique of a single screw compressor used for a refrigerator or an air conditioner, and more particularly to a single screw compressor having a single gate rotor meshing with a screw rotor and a refrigeration cycle apparatus having the same.

In a single screw compressor, a twin having a screw rotor having a screw groove formed on the outer peripheral surface and two gate rotors, and two gate rotors meshing with the screw groove of the screw rotor to form a pair of compression chambers A gate rotor system is known. In the twin gate rotor system, a pair of compression chambers are formed above and below the rotating shaft of the screw rotor. In general, the rotating shaft is driven by an electric motor, and a series of operations from suction to discharge is performed in each compression chamber. The

The refrigerant is sucked into the pair of compression chambers formed above and below the rotating shaft at the same timing, and the volume change rate of the pair of compression chambers is the same from the start of suction to the completion of discharge. For this reason, the transition of the magnitude of the internal pressure due to the compressed gas in the pair of compression chambers from the start of suction to the completion of discharge is the same. Therefore, the twin gate rotor type single screw compressor cancels the action of the pressure in the compression chamber between the pair of compression chambers, and therefore has a characteristic that a gas load in the radial direction of the rotating shaft does not occur. Therefore, in the twin gate rotor type single screw compressor, there is known an advantage that the bearing supporting the rotating shaft can be reduced in size. However, since there are two gate rotors, there is a problem that the number of parts increases and the number of assembly steps is also large.

On the other hand, a single screw compressor includes a screw rotor having a screw groove formed on the outer peripheral surface and one gate rotor, and one gate rotor meshes with the screw groove of the screw rotor to form one compression chamber. There is also a method of forming (see, for example, Patent Document 1). The method with one gate rotor is hereinafter referred to as a mono-gate rotor method with respect to the twin gate rotor method with two gate rotors. In the monogate rotor system, since there is one gate rotor, there is an advantage that the number of parts and the number of assembly steps can be reduced.

Japanese Patent No. 5383303

However, in Patent Document 1, since the compression chamber is formed below the rotation shaft, there are the following problems. That is, at the time of so-called liquid back where the liquid refrigerant flows into the single screw compressor, the liquid refrigerant flows into the bottom part of the casing constituting the outer shell of the single screw compressor by its own weight. For this reason, when the compression chamber is formed below the rotation shaft, there is a drawback that it is easy to suck the refrigerant accumulated in the bottom of the sealed container. This problem can also occur in the same way, for example, when starting from a state where liquid refrigerant has accumulated in the sealed container after long-term operation stop. Then, when the liquid refrigerant is sucked into the compression chamber and compressed, the pressure in the compression chamber increases, and the rotation shaft greatly bends according to the pressure, and the outer periphery of the screw rotor and the inner periphery of the casing that houses the screw rotor. There is a problem of seizure due to contact with.

The present invention has been made in view of the above points, and in a monogate rotor type single screw compressor, there is provided a single screw compressor and a refrigeration cycle apparatus capable of suppressing suction of liquid refrigerant into a compression chamber. The purpose is to obtain.

A single screw compressor according to the present invention is engaged with an electric motor, a rotating shaft driven by the electric motor, a screw rotor attached to the rotating shaft and having a plurality of screw grooves on an outer peripheral surface, and a screw groove of the screw rotor. A compression chamber in a space surrounded by the screw groove, the gate rotor and the casing, comprising a single gate rotor rotating with the rotation of the screw rotor, and an electric motor, a rotating shaft, a screw rotor, and a casing containing the gate rotor. The casing divides the inside of the casing into a first space in which a motor is accommodated and fluid flows in from the outside, and a second space on the downstream side of the first space where the compression chamber is located. The suction port that has the partition and communicates the first space and the second space is higher than the height position of the axis of the rotation shaft in the partition. Together provided towards the compression chamber in which is positioned higher than the height position of the axis of the rotating shaft.

A refrigeration cycle apparatus according to the present invention includes the single screw compressor, a condenser, a decompression device, and an evaporator.

According to the present invention, the inside of the casing is separated into the first space into which the fluid flows from the outside and the second space in which the compression chamber is located, and the suction port and the compression chamber communicating the first space and the second space. Is positioned above the height position of the axis of the rotating shaft, so that the suction of the liquid refrigerant into the compression chamber can be suppressed.

It is a refrigerant circuit figure of the refrigerating cycle device provided with the single screw compressor concerning Embodiment 1 of the present invention. 1 is a schematic cross-sectional view of a monogate rotor type single screw compressor according to Embodiment 1 of the present invention. FIG. 3 is a schematic cross-sectional view along AA in FIG. 2. FIG. 3 is a schematic cross-sectional view taken along the line BB of FIG. It is a figure which shows the operation | movement flowchart of the single screw compressor which concerns on Embodiment 1 of this invention. It is explanatory drawing of the modification of the single screw compressor which concerns on Embodiment 1 of this invention, and is a schematic perspective view which shows the discharge outlet vicinity. It is a figure which shows the operation | movement flowchart at the time of the oil return operation | movement in the refrigerating-cycle apparatus provided with the single screw compressor which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
1 is a refrigerant circuit diagram of a refrigeration cycle apparatus including a single screw compressor according to Embodiment 1 of the present invention. In FIG. 1 and the drawings shown below, the same reference numerals are the same or equivalent, and this is common throughout the entire specification. Furthermore, the forms of the constituent elements shown in the entire specification are merely examples and are not limited to these descriptions.

The refrigeration cycle apparatus 100 includes a single screw compressor 101, a condenser 103, a decompression device 104, and an evaporator 105, and includes a refrigerant circuit in which these are sequentially connected by refrigerant piping.

The single screw compressor 101 sucks a refrigerant as a fluid and compresses the refrigerant to a high temperature and high pressure state. The single screw compressor 101 is driven by supplying electric power from an electric power supply source (not shown) to the electric motor 102. The electric motor 102 may be a constant speed machine with a constant rotation speed, or an inverter type that is driven so that the operation capacity can be adjusted by changing the rotation speed. Assumed. Note that the fluid may be air in addition to the refrigerant accompanying the phase change.

The condenser 103 cools and condenses the refrigerant gas discharged from the single screw compressor 101. The decompression device 104 squeezes and expands the refrigerant liquid flowing out of the condenser 103, and includes an electronic expansion valve or a capillary tube.

A suction temperature sensor 120 and a suction pressure sensor 121 are provided on the suction side of the single screw compressor 101. The suction temperature sensor 120 detects the temperature of the suction gas sucked into the single screw compressor 101. The suction pressure sensor detects the pressure of the suction gas sucked into the single screw compressor 101. Detection values detected by the suction temperature sensor 120 and the suction pressure sensor 121 are output to the control device 110 described later.

The refrigeration cycle apparatus 100 further includes a control device 110. The control device 110 performs opening degree control of the decompression device 104, position control of a slide valve 6 (see FIG. 2) described later, and control of the entire refrigeration cycle apparatus 100. Further, the control device 110 detects a liquid back to the suction side of the single screw compressor 101, and performs opening / closing control of a solenoid valve 9 (see FIG. 2) described later according to the detection result of the liquid back. The control device 110 can be configured by hardware such as a circuit device that realizes the function, or can be configured by an arithmetic device such as a microcomputer or a CPU and software executed thereon.

(Explanation of refrigerant circuit operation)
Next, operation | movement of the refrigerating-cycle apparatus 100 of Embodiment 1 is demonstrated with reference to FIG.

The single screw compressor 101 sucks and compresses refrigerant gas, which is a gaseous refrigerant, and then discharges it. The discharge gas discharged from the single screw compressor 101 is cooled by the condenser 103. The refrigerant cooled by the condenser 103 is decompressed by the decompression device 104 and expands. And the refrigerant | coolant which flowed out from the decompression device 104 is heated with the evaporator 105, and becomes refrigerant gas. The refrigerant gas flowing out of the evaporator 105 is sucked into the single screw compressor 101.

(Single screw compressor)
Hereinafter, a single screw compressor 101 according to Embodiment 1 of the present invention will be described with reference to FIGS.

FIG. 2 is a schematic cross-sectional view of a monogate rotor type single screw compressor according to Embodiment 1 of the present invention. 2 is a schematic cross-sectional view of the single screw compressor 101 installed on the installation surface cut along a plane parallel to the installation surface, and the cut surface is viewed from above. The vertical direction in FIG. This corresponds to the left-right direction of the single screw compressor 101. FIG. 3 is a schematic cross-sectional view taken along the line AA in FIG. 4 is a schematic cross-sectional view taken along the line BB of FIG.

The single screw compressor 101 is a single screw compressor having one screw rotor 3 and has a monogate rotor structure having one gate rotor 4. The single screw compressor 101 includes a casing 1, one screw rotor 3, one gate rotor 4 meshing with the screw rotor 3, an electric motor 102 that rotationally drives the screw rotor 3, a slide valve 6, and the like. It has. The casing 1 accommodates the screw rotor 3, the gate rotor 4, the electric motor 102, the slide valve 6, and the like.

In the casing 1, a substantially cylindrical space is formed, and a substantially columnar screw rotor 3 is arranged in this space. One end of the screw rotor 3 is a refrigerant suction side (right side in FIG. 2), and the other end is a discharge side (left side in FIG. 2). A plurality of spiral screw grooves 3 a are formed on the outer peripheral surface of the screw rotor 3. A rotating shaft 5 is attached to the center of the screw rotor 3 so as to rotate together. The rotating shaft 5 is rotatably supported by a bearing 5 a provided in the casing 1.

Further, an electric motor 102 is connected to the end of the rotating shaft 5 on the side opposite to the bearing 5a. The electric motor 102 includes a stator 102a that is inscribed and fixed to the casing 1, and a motor rotor 102b that is disposed inside the stator 102a. And the rotating shaft 5 is connected with the motor rotor 102b, and the screw rotor 3 is rotationally driven.

The gate rotor 4 has a disk shape, and a plurality of teeth 4a are formed on the outer periphery. In the gate rotor 4, the plurality of teeth 4 a are engaged with the screw grooves 3 a, and rotates with the rotation of the screw rotor 3. The space surrounded by the teeth 4 a of the gate rotor 4, the screw groove 3 a and the casing 1 becomes the compression chamber 7.

The casing 1 has an internal space in which a low-pressure gas refrigerant flows from the evaporator 105 of the refrigerant circuit, the first space 31 in which the electric motor 102 is accommodated, and the downstream of the first space 31 in the compression chamber 7. And the second space 32 in which is located is separated by a partition wall 1b which is a part of the casing 1. The casing 1 has a suction port (not shown) through which a low-pressure gas refrigerant is introduced from the refrigerant circuit, and a discharge port (not shown) that discharges compressed gas to the refrigerant circuit. 31 communicates with a suction port (not shown), and the second space 32 communicates with a discharge port (not shown). A suction port 8 that communicates the first space 31 and the second space 32 is formed through the partition wall 1b. The suction gas introduced into the first space 31 enters the second space 32 through the suction port 8. be introduced. That is, the suction port 8 is one of flow paths for guiding the refrigerant flowing into the casing 1 to the compression chamber 7.

In addition, the casing 1 is connected to the first space 31 and the second space 32 at least at one location via the outside of the casing 1, and the piping that supplies the oil accumulated in the first space 31 to the second space 32. 10 is connected. The pipe 10 is provided with an electromagnetic valve 9 that opens and closes the flow path of the pipe 10. Since oil accumulates at the bottom of the casing 1, the pipe 10 and the electromagnetic valve 9 are provided below the height position of the axis O <b> 1 of the rotating shaft 5.

The single screw compressor 101 is provided with a slide valve 6 for adjusting the operating capacity. The slide valve 6 is formed in a rod shape having a crescent-shaped cross section. A slide groove 1aa extending in the direction of the rotation axis 5 of the screw rotor 3 is formed on the inner peripheral surface 1a side of the casing 1, and a slide valve 6 is slidably accommodated in the slide groove 1aa. A rod (not shown) is fixed to the end face of the slide valve 6 and is movable in the axial direction parallel to the rotary shaft 5. The position of the slide valve 6 is adjusted by a dedicated drive device (not shown).

The second space 32 in the casing 1 is further partitioned into a low pressure side that is a refrigerant suction side to the compression chamber 7 and a high pressure side that is a refrigerant discharge side. A bypass passage (not shown) for communicating with the suction side in the space 32 is formed. As the slide valve 6 moves, the opening area of the bypass passage (not shown) changes. That is, when the slide valve 6 moves, the opening area of the bypass passage (not shown) changes, and the flow rate of the fluid (refrigerant) sent to the suction side through the bypass passage (not shown) changes. As a result, the flow rate of the fluid compressed and discharged in the compression chamber 7 changes, and the flow rate of the fluid discharged from the single screw compressor 101, that is, the operating capacity changes.

Next, a characteristic configuration of the first embodiment will be described.
The first embodiment is intended to suppress the liquid refrigerant from being sucked into the compression chamber 7 at the time of liquid back or at the start-up after long-term operation stop, and adopts the following configuration. is doing. That is, as shown in FIG. 3, the suction port 8 is disposed above the height position of the axis O1 of the rotary shaft 5 in the partition wall 1b. When liquid refrigerant flows into the single screw compressor 101 from the evaporator 105 of the refrigerant circuit, the liquid refrigerant accumulates at the bottom in the first space 31 due to its own weight. For this reason, by providing the suction port 8 above the partition 1 b, the liquid refrigerant that has flowed into the first space 31 can be made difficult to flow into the second space 32.

In addition, here, as shown in FIG. 4, a configuration in which the suction ports 8 are provided at three positions with intervals in the circumferential direction of the rotating shaft 5 is shown, but the number is arbitrary. Here, the suction port 8 has a long hole shape extending in the circumferential direction of the rotating shaft 5, but the shape is not limited as long as a necessary opening cross-sectional area is secured. The opening cross-sectional area of the suction port 8 is adjusted to ensure a necessary flow rate in consideration of the displacement of the compression chamber 7, the rotational speed of the rotary shaft 5, and the density of the working fluid.

In the first embodiment, the compression chamber 7 is also disposed above the height position of the axis O1 of the rotary shaft 5 in the same manner as the suction port 8. This is due to the following reason. The inflow of the liquid refrigerant from the first space 31 to the second space 32 is reduced by providing the suction port 8 upward, but is not completely eliminated. Accordingly, the liquid refrigerant that has flowed into the second space 32 accumulates at the bottom of the second space 32. For this reason, when the compression chamber 7 is below the height position of the axis O1 of the rotation shaft 5, the liquid refrigerant is easily sucked. Therefore, the compression chamber 7 is also disposed above the height position of the axis O <b> 1 of the rotating shaft 5, similarly to the suction port 8.

Note that when the compression chamber 7 is disposed above the height position of the axis O1 of the rotary shaft 5, the gate rotor 4 may be disposed as follows. That is, the axial center O2 of the gate rotor 4 is disposed so as to face the direction orthogonal to the axial center O1 at a position separated from the axial center O1 of the rotating shaft 5 of the screw rotor 3. Further, the gate rotor 4 may be arranged so that the radial plane of the gate rotor 4 faces in the range from 12:00 to 3 o'clock of the timepiece when the rotation shaft 5 of the screw rotor 3 is regarded as the center of the timepiece. . With this configuration, one compression chamber 7 can be formed above the height position of the axis O1 of the rotary shaft 5. Here, as shown in FIG. 3, the gate rotor 4 is arranged so that the radial plane of the gate rotor 4 faces the 3 o'clock direction of the watch.

Incidentally, the refrigerant that has flowed into the first space 31 contains oil for lubricating the sliding portion such as the bearing 5 a of the rotating shaft 5, and the oil also collects at the bottom of the first space 31. Therefore, it is necessary to supply oil accumulated at the bottom of the first space 31 to the second space 32 so that the sliding portion does not run out of oil. Therefore, the oil accumulated at the bottom of the first space 31 is supplied to the second space 32 through the pipe 10. When the electromagnetic valve 9 is opened when the single screw compressor 101 is in the liquid back state, the liquid is passed through the pipe 10. There is a possibility that the refrigerant flows into the second space 32 and the liquid refrigerant is sucked into the compression chamber 7. Therefore, in the first embodiment, control is performed so that the electromagnetic valve 9 is closed when the liquid back state is set, and is opened when the liquid back state is not set.

(Description of operation)
FIG. 5 is a diagram showing an operation flowchart of the single screw compressor according to Embodiment 1 of the present invention. Hereinafter, the operation of the single screw compressor 101 will be described with reference to FIG.
First, the control device 110 activates the single screw compressor 101 with the operation capacity minimized (step S1). This is intended to reduce the load on the motor 102 at the time of startup, and is a normal control. Here, in order to minimize the operating capacity, the position of the slide valve 6 is adjusted so that the opening area of the bypass passage from the compression chamber 7 to the suction side is maximized. That is, within the range in which the position of the slide valve 6 can be adjusted, the position of the slide valve 6 is adjusted to a position where the displacement amount of the single screw compressor 101 is minimized, and the single screw compressor 101 is started after the adjustment.

Also, the solenoid valve 9 is closed at the time of activation (step S1). This prevents liquid refrigerant from flowing into the second space 32 through the pipe 10 because the liquid refrigerant may be accumulated in the first space 31 at the time of startup after a long-term operation stop, for example. Is intention.

When the rotation speed of the electric motor 102 reaches the set rotation speed (step S2), the operation is performed with the operation capacity corresponding to the load on the use side of the refrigerant circuit (step S3). That is, the control device 110 adjusts the position of the slide valve 6 so as to obtain an operation capacity corresponding to the load on the use side.

Then, after the rotational speed of the electric motor 102 reaches the set rotational speed, that is, during the steady operation after the start-up time, the control device 110 performs opening / closing control of the electromagnetic valve 9 according to the liquid back detection result (step S4 to step S4). S6). This will be specifically described below.

The control device 110 determines whether or not a liquid back has occurred (step S4). If it is determined that a liquid back has occurred, the controller 110 transfers the liquid refrigerant from the first space 31 to the second space 32 via the pipe 10. In order to avoid inflow, the electromagnetic valve 9 is closed (step S5). Here, whether or not the liquid back has occurred is determined based on the degree of superheat of the intake gas temperature. That is, when the degree of superheating of the intake gas temperature is less than a preset value, it is determined that a liquid back has occurred. On the other hand, when the state in which the superheat degree of the intake gas temperature is equal to or higher than the set value continues for a preset time, it is determined that no liquid back has occurred. The set value may be 0 ° C., or may be a temperature higher than 0 ° C., for example, 3 ° C. for safe control. Note that the degree of superheating of the intake gas temperature is obtained by subtracting the evaporation temperature from the detected value of the intake temperature sensor 120. The evaporation temperature is obtained by converting the pressure of the suction pressure sensor 121 into a saturation temperature.

On the other hand, when it is determined that the liquid back has not occurred, the control device 110 opens the electromagnetic valve 9 (step S6).

After controlling the solenoid valve 9 by step S5 or step S6, it returns to step S4 again and repeats the same process. Therefore, the electromagnetic valve 9 is maintained in the closed state while the liquid back is generated, and the electromagnetic valve 9 is maintained in the open state while the liquid back is not generated.

Here, consider a case where an event that causes liquid back occurs, for example, when the single screw compressor 101 is in steady operation and no liquid back is generated, for example, the refrigerant circuit is additionally charged with refrigerant. . In this case, the degree of superheating of the intake gas temperature decreases and falls below the set value. Therefore, it is determined in step S4 that a liquid back has occurred, and the solenoid valve 9 is switched from open to closed. When the additional charging of the refrigerant is completed, the degree of superheat of the intake gas temperature increases. Immediately after the additional charging of the refrigerant, the superheat degree of the intake gas temperature may fluctuate up and down without being stable, but gradually becomes stable. When the degree of superheating of the intake gas temperature is stabilized for a set time, it is determined in step S4 that no liquid back has occurred, and the solenoid valve 9 is switched from closed to open.

As described above, when the solenoid valve 9 is opened in a state where no liquid back is generated, the suction gas flows from the first space 31 to the second space 32 through the pipe 10, and the oil mist is added to the flow of the suction gas. And oil is sucked into the compression chamber 7 together with the refrigerant. Then, the oil mist sucked into the single screw compressor 101 flows into the oil separator (not shown) built in the single screw compressor 101 together with the compressed gas. The oil separated from the refrigerant by an oil separator (not shown) is supplied to the sliding part in the single screw compressor 101, and the oil can be circulated.

(Effect of Embodiment 1)
As described above, according to the first embodiment, the suction port 8 is provided above the height position of the axis O1 of the rotation shaft 5. For this reason, even if the liquid refrigerant is accumulated in the first space 31 at the time of liquid back or at the start from the long-term operation stop, the liquid refrigerant in the first space 31 flows into the second space 32 where the compression chamber 7 is located. Can be suppressed. While the flow of the liquid refrigerant is suppressed to the second space 32 while being somewhat suppressed, the compression chamber 7 is also located above the height position of the axis O1 of the rotary shaft 5 like the suction port 8. Therefore, the liquid refrigerant can be prevented from being sucked into the compression chamber 7. As a result, an increase in the internal pressure of the compression chamber 7 due to liquid compression can be prevented, so that the deflection of the rotating shaft 5 can be kept small, and the contact between the outer periphery of the screw rotor 3 and the inner periphery of the casing 1 can be prevented, thereby ensuring high reliability. There is an effect that can be done.

Further, since the inside of the casing 1 is separated into the first space 31 and the second space 32 by the partition wall 1b, it is necessary to supply the oil in the first space 31 to the second space 32. This can be done with the pipe 10 provided. And the opening / closing timing of the electromagnetic valve 9 provided in the pipe 10 is controlled by whether or not the liquid back is generated, and when the liquid back is generated, the electromagnetic valve 9 is closed. did. For this reason, it can prevent that a liquid refrigerant flows in into the 2nd space 32 from the 1st space 31 via the piping 10, As a result, the suction | inhalation of the liquid refrigerant to the compression chamber 7 can be suppressed.

When the liquid back is not generated, the electromagnetic valve 9 is opened, so that the oil mist flows along with the suction gas refrigerant from the first space 31 to the second space 32 and is sucked into the compression chamber 7. I can make it. The oil sucked into the compression chamber 7 flows out of the compression chamber 7 together with the refrigerant gas. However, the oil can be captured again in an oil separator (not shown) in the single screw compressor 101, and the compression chamber The oil can be returned to 7. Therefore, there is an effect that can be effectively used for lubrication for lubricating the sliding portion.

Further, since the electromagnetic valve 9 is closed at the time of startup, when the liquid back is generated at the time of startup and when the liquid refrigerant is stored in the first space 31, the liquid refrigerant passes through the pipe 10 from the first space 31 to the second time. Inflow into the space 32 can be prevented. Note that here, the solenoid valve 9 is controlled to be closed regardless of the occurrence of liquid back at the time of startup, but this control is intended to be safety-side control with a view to startup after long-term operation stoppage. It is. For example, in the case of activation after a short stop, it may be determined to determine whether or not a liquid back has occurred at the time of activation, and to open the solenoid valve 9 when it is determined that no liquid back has occurred.

From the above, it is possible to obtain the single screw compressor 101 that can suppress the suction of the liquid refrigerant into the compression chamber 7 while circulating oil in the single screw compressor 101 and can ensure reliability.

(Modification)
The single screw compressor 101 may be modified as follows with respect to the configuration shown in FIGS. In this case, the same effect can be obtained.

The single screw compressor 101 according to the first embodiment uses a constant speed electric motor 102 to adjust the amount of refrigerant gas sucked into the compression chamber 7 by the slide valve 6, that is, to control the operation capacity. The operating capacity control method is not limited to this method. In addition, for example, the operation capacity control may be performed by rotation speed control using the inverter type electric motor 102 instead of the slide valve 6.

Further, when the inverter type electric motor 102 is used as described above, a variable VI valve which is a slide valve that adjusts the timing of discharge from the compression chamber 7 and makes the volume ratio variable is used. Here, the volume ratio indicates the ratio between the volume of the compression chamber 7 at the completion of suction (at the start of compression) and the volume of the compression chamber 7 just before the discharge.

FIG. 6 is an explanatory view of a modification of the single screw compressor according to Embodiment 1 of the present invention, and is a schematic perspective view showing the vicinity of the discharge port.
The variable VI valve 21 forms a part of the discharge port 11, is connected to a rod 21 a and a drive device (not shown), and is movable in the direction of the rotation axis of the screw rotor 3. When the variable VI valve 21 moves to the suction side (the back side in FIG. 5), the volume ratio decreases, and when the variable VI valve 21 moves to the discharge side (the front side in FIG. 5), the volume ratio increases. Become. Further, the electric motor 102 is configured to be able to adjust the rotation speed by inverter control. Thereby, the operating capacity of the single screw compressor 101, that is, the flow rate of the refrigerant discharged from the single screw compressor 101 is controlled according to the load on the usage side of the refrigerant circuit. At that time, the variable VI valve 21 is controlled so as to have a volume ratio (compression ratio) at which an optimum compression efficiency is obtained with respect to the operation capacity set according to the load on the use side.

The control of the electromagnetic valve 9 in this modification is the same as the flowchart shown in FIG. 5, and the adjustment of the operation capacity in step S1 and step S3 is different. That is, in step S1, the rotational speed of the electric motor 102 is set to the lowest rotational speed in the operable range, and the position of the variable VI valve 21 is adjusted, so that the volume ratio becomes the lower limit volume ratio of the volume ratio settable range. Like that. In step S3, the rotational speed of the electric motor 102 is adjusted to a rotational speed corresponding to the load on the use side, and the position of the variable VI valve 21 is adjusted to increase energy efficiency according to the operating pressure ratio. To do.

Embodiment 2. FIG.
In the second embodiment, a full liquid evaporator is used as the evaporator 105 of the refrigeration cycle apparatus 100 shown in FIG. Other configurations are the same as those of the first embodiment. The following description will focus on the differences of the second embodiment from the first embodiment. Configurations not described in the second embodiment are the same as those in the first embodiment.

Oil that could not be separated from the refrigerant by an oil separator (not shown) in the single screw compressor 101 flows out into the refrigerant circuit outside the single screw compressor 101 and is stored in the full liquid evaporator 105. Go. For this reason, in the refrigeration cycle apparatus 100 using the full liquid evaporator 105, the oil in the full liquid evaporator 105 is used to secure the amount of oil necessary for lubrication of the sliding portion in the single screw compressor 101. It needs to be returned into the single screw compressor 101. Therefore, an oil return operation is performed in which the oil in the full liquid evaporator 105 is returned to the single screw compressor 101.

Since the liquid refrigerant contains more oil than the gas refrigerant, the liquid refrigerant flows into the single screw compressor 101 when returning the oil in the full liquid evaporator 105 into the single screw compressor 101. Thus, the oil can be easily and efficiently returned to the single screw compressor 101. Therefore, in the oil return operation, the temperature of the suction gas sucked into the single screw compressor 101 is lowered to the evaporation temperature that is the saturation temperature of the refrigerant in the full-liquid evaporator 105 to make the suction gas refrigerant a liquid refrigerant. The operation of returning the oil in the evaporator 105 to the single screw compressor 101 together with the liquid refrigerant is performed. In order to lower the intake gas temperature to the evaporation temperature, the opening of the expansion valve as the decompression device 104 may be increased.

The rotational speed of the single screw compressor 101 during the oil return operation is lower than the maximum rotational speed at which the single screw compressor 101 can be operated. This is for the purpose of preventing the liquid refrigerant from suddenly returning into the single screw compressor 101.

In the oil return operation, the liquid refrigerant returns from the full liquid evaporator 105 into the single screw compressor 101. Therefore, when the single screw compressor 101 has a configuration in which the liquid refrigerant flows directly into the compression chamber 7, the reliability of the single screw compressor 101 due to liquid compression is reduced. However, as described above, the single screw compressor 101 used here has a structure that suppresses the liquid refrigerant from directly flowing into the compression chamber 7 even when a liquid back occurs, and thus the reliability is impaired. There is no.

The operation of the second embodiment will be described. The refrigeration cycle apparatus 100 according to the second embodiment performs the operation according to the flowchart shown in FIG. 5 in the same manner as in the first and second embodiments when starting the single screw compressor 101 and during the steady operation. The following operation shown in FIG. 7 is performed.

FIG. 7 is a diagram showing an operation flowchart at the time of oil return operation in the refrigeration cycle apparatus including the single screw compressor according to Embodiment 2 of the present invention.
When determining that the oil return operation is being performed (step S11), the control device 110 closes the electromagnetic valve 9 (step S12). Thereby, liquid refrigerant can be prevented from flowing into the compression chamber 7. When the controller 110 determines that the oil return operation is finished and no liquid back has occurred (step S13), the controller 110 opens the electromagnetic valve 9 (step S14).

(Effect of Embodiment 2)
In the second embodiment, the same effect as in the first embodiment is obtained, and the suction refrigerant is caused to flow into the single screw compressor 101 in the state of liquid refrigerant in the oil return operation. The oil can be easily returned to.

And by closing the solenoid valve 9 during the oil return operation, the liquid refrigerant can be prevented from flowing into the second space 32 via the pipe 10. Therefore, there is an effect that oil can be easily returned from the full liquid evaporator 105 into the single screw compressor 101 while ensuring the reliability of the single screw compressor 101.

1 casing, 1a inner peripheral surface, 1aa slide groove, 1b partition wall, 3 screw rotor, 3a screw groove, 4 gate rotor, 4a teeth, 5 rotating shaft, 5a bearing, 6 slide valve, 7 compression chamber, 8 intake port, 9 Solenoid valve, 10 pipe, 11 discharge port, 21 variable VI valve, 21a rod, 31 1st space, 32 2nd space, 100 refrigeration cycle device, 101 single screw compressor, 102 electric motor, 102a stator, 102b motor rotor, 103 Condenser, 104 decompression device, 105 evaporator (full liquid evaporator), 110 control device, 120 suction temperature sensor, 121 suction pressure sensor, O1 axis, O2 axis.

Claims

An electric motor,
A rotating shaft driven by the electric motor;
A screw rotor attached to the rotating shaft and having a plurality of screw grooves on the outer peripheral surface;
One gate rotor that engages with the screw groove of the screw rotor and rotates as the screw rotor rotates;
A casing for housing the electric motor, the rotating shaft, the screw rotor, and the gate rotor;
A space surrounded by the screw groove, the gate rotor and the casing constitutes a compression chamber,
The casing is a partition that accommodates the electric motor and separates the casing into a first space into which a fluid flows from the outside and a second space on the downstream side of the first space where the compression chamber is located. Have
A suction port that communicates the first space and the second space is provided above the height position of the axis of the rotary shaft in the partition wall, and the compression chamber is the height of the axis of the rotary shaft. Single screw compressor located above the position.
The gate rotor is disposed such that its own axis is oriented in a direction perpendicular to the axis of the rotation axis of the screw rotor, and the rotation axis of the screw rotor is regarded as the center of a watch. The single screw compressor according to claim 1, wherein the gate rotor is arranged so that a radial plane of the gate rotor sometimes faces within a range from 12 o'clock to 3 o'clock of the timepiece.
At least one is provided below the height position of the axis of the rotating shaft, the first space and the second space are communicated via the outside of the casing, and the oil in the first space is Piping to be supplied to the second space;
The single screw compressor according to claim 1, further comprising an electromagnetic valve provided in the pipe and opening and closing a flow path of the pipe.
The single screw compressor according to claim 3, wherein the solenoid valve is opened when a liquid back to the single screw compressor is not generated, and is closed when a liquid back is generated.
4. The single screw compressor according to claim 3, wherein the solenoid valve is closed at the time of startup.
A refrigeration cycle apparatus comprising the single screw compressor according to any one of claims 1 to 5, a condenser, a decompression device, and an evaporator.
A control device for controlling the electromagnetic valve;
When the degree of superheat of the intake gas temperature of the single screw compressor is less than a set value during steady operation, the control device closes the solenoid valve, and the state where the degree of superheat is equal to or greater than the set value continues for a set time. The refrigeration cycle apparatus according to claim 6, which is dependent on claim 4, wherein the electromagnetic valve is opened.
The refrigeration cycle apparatus according to claim 6 or 7, wherein the evaporator is a full liquid evaporator.
The control device controls the pressure reducing device to close the solenoid valve during the oil return operation for lowering the suction gas temperature to the saturation temperature of the refrigerant in the full liquid evaporator, the oil return operation is completed, and the liquid return operation is completed. The refrigeration cycle apparatus according to claim 8, which is dependent on claim 7 and is opened when no back is generated.