WO2018037469A1

WO2018037469A1 - Screw compressor and refrigeration cycle device

Info

Publication number: WO2018037469A1
Application number: PCT/JP2016/074443
Authority: WO
Inventors: 克也前田
Original assignee: 三菱電機株式会社
Priority date: 2016-08-23
Filing date: 2016-08-23
Publication date: 2018-03-01
Also published as: EP3505765A4; EP3505765A1; CN109642579B; EP3505765B1; CN109642579A

Abstract

A screw compressor equipped with: a casing in which is formed a refrigerant liquid flow path through which a refrigerant liquid passes from the outside; a screw rotor on the outer circumferential surface of which multiple screw grooves forming a compression chamber are formed, and which is arranged so as to rotate inside the casing; and a slide valve that is provided between the casing and the screw rotor, and that slides in the direction of the rotary shaft of the screw rotor. The casing and/or the slide valve are provided with an oil injection port for supplying oil to the screw grooves. The slide valve has a refrigerant liquid injection flow path enabling the refrigerant liquid flow path to communicate with the screw grooves, and moves between a first position, in which the refrigerant liquid injection flow path communicates with the screw grooves from immediately before compression to immediately after compression, and a second position, which is a position in which the refrigerant liquid injection flow path communicates with the screw grooves in an intake stroke before compression begins, and the position of the refrigerant liquid injection flow path in the direction of the rotary shaft is closer to the oil injection port than the first position.

Description

Screw compressor and refrigeration cycle apparatus

The present invention relates to a screw compressor and a refrigeration cycle apparatus used for refrigerant compression of a refrigerator, for example.

The single screw compressor accommodates a screw rotor having a plurality of spiral screw grooves on the outer peripheral surface and two disk-shaped gate rotors having a plurality of teeth in a casing. A compression chamber is formed by a space surrounded by the casing, the screw groove of the screw rotor, and the teeth of the gate rotor. Then, as the screw rotor rotates, the teeth of the gate rotor move through the screw grooves of the screw rotor, and the operation of reducing the volume of the compression chamber after the expansion is repeated. While the volume of the compression chamber increases, the refrigerant is sucked into the compression chamber, and when the volume of the compression chamber starts to be reduced, the sucked refrigerant is compressed. When the screw groove, which is a compression chamber, communicates with the discharge port, the compressed high-pressure refrigerant is discharged from the compression chamber.

In this type of single screw compressor, the discharge temperature of the discharged refrigerant gas discharged from the compressor becomes high under high operating conditions with high and low differential pressures or when the motor speed is increased by an inverter. When the discharge temperature becomes high, there is a possibility that the screw rotor is thermally expanded and comes into contact with the casing and seizes.

Therefore, conventionally, when the discharge temperature is higher than the set temperature, the oil contained in the discharge refrigerant gas discharged from the compressor is separated by an oil separator, and the separated oil is cooled by an oil cooler to form a compression chamber. By injecting into the screw groove, an increase in discharge temperature is suppressed (see, for example, Patent Document 1).

Japanese Utility Model Publication No. 63-130686

By the way, the temperature of the suction gas sucked into the compressor is lower than the temperature of the discharge gas. For this reason, during steady operation, the screw rotor can be cooled by sucking the suction gas into the screw groove of the screw rotor. However, during unsteady operation, the temperature of the suction gas itself sucked into the compressor is high, and the cooling effect of the screw rotor by the suction gas is reduced. The unsteady operation is an operation in which the degree of superheat of the suction gas (hereinafter referred to as “intake SH”) rapidly increases or becomes higher than the intake SH in the steady operation, for example, at the start of operation. When the cooling effect of the screw rotor is thus reduced, there is a concern about seizure due to thermal expansion of the screw rotor. For this reason, it is required to prevent seizure of the screw rotor during unsteady operation.

Patent Document 1 describes that the oil separated by the oil separator is cooled and injected into the compression chamber to lower the discharge temperature, but the temperature rise of the oil during unsteady operation is not studied. . During unsteady operation, the discharge temperature rises and the temperature of the oil separated by the oil separator inevitably increases. For this reason, even if it cools with an oil cooler, oil cannot fully be cooled, but it will be supplied to a compression chamber with high temperature. Further, as described above, since the temperature of the suction gas becomes high during the unsteady operation, there still remains a problem of seizure of the screw rotor. Furthermore, even in a configuration without an oil cooler, there is a possibility that the screw rotor will seize because high-temperature oil is directly injected into the compression chamber during unsteady operation.

The present invention has been made in order to solve the above-described problems, and can suppress an increase in discharge temperature and can suppress seizure of the screw rotor during unsteady operation. An object is to provide a compressor and a refrigeration cycle apparatus.

In the screw compressor according to the present invention, a casing in which a refrigerant liquid flow path through which a refrigerant liquid from the outside passes is formed, and a plurality of screw grooves constituting a compression chamber are formed on the outer peripheral surface so as to rotate in the casing. A screw rotor disposed between the casing and the screw rotor, and a slide valve that slides in the direction of the rotation axis of the screw rotor. An oil injection port to be supplied is provided, and the slide valve has a refrigerant liquid injection channel for communicating the refrigerant liquid channel with the screw groove, and the refrigerant liquid injection channel is provided between immediately before and after the start of compression. The first position to be communicated with the screw groove and the refrigerant liquid injection channel are communicated with the screw groove in the suction stroke before the compression is started. A location, the position of the rotational axis than the first position is moved to a second position closer to the oil injection port.

A refrigeration cycle apparatus according to the present invention includes a refrigerant circuit in which the screw compressor, the condenser, the main decompressor, and the evaporator are connected in order.

According to the present invention, the slide valve is positioned at the first position, and the liquid injection is started immediately before and after the start of compression, thereby suppressing an increase in discharge temperature. Also, the seizure of the screw rotor during unsteady operation is suppressed by liquid injection from the position where the slide valve is located at the second position and the position in the rotation axis direction is closer to the oil injection port than the first position. it can.

It is a refrigerant circuit figure of the refrigerating cycle device provided with the screw compressor concerning Embodiment 1 of the present invention. It is a schematic block diagram of the screw compressor which concerns on Embodiment 1 of this invention. FIG. 4 is a development view of the outer periphery of the screw rotor of the screw compressor according to Embodiment 1 of the present invention, and shows the positional relationship between the screw groove and the injection port when the slide valve is disposed at the first position on the discharge side. It is. FIG. 4 is a development view of the outer surface of the screw rotor of the screw compressor according to Embodiment 1 of the present invention, and shows the positional relationship between the screw groove and the injection port when the slide valve is arranged at the second position on the suction side. It is. It is a figure which shows the compression principle of the screw compressor which concerns on Embodiment 1 of this invention. It is a figure which shows the flowchart of the liquid injection control in the refrigerating-cycle apparatus provided with the screw compressor which concerns on Embodiment 1 of this invention. It is a refrigerant circuit figure of the refrigerating cycle device concerning Embodiment 2 of the present invention.

Embodiment 1 FIG.
FIG. 1 is a refrigerant circuit diagram of a refrigeration cycle apparatus including a 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 refrigerant circuit in which a screw compressor 102, a condenser 104, a main expansion valve 105, and an evaporator 106 are connected in order by refrigerant piping. The refrigeration cycle apparatus 100 further includes a refrigerant liquid pipe 108 that branches from between the condenser 104 and the main expansion valve 105 and is connected to the screw compressor 102. The refrigerant liquid pipe 108 is provided with a flow rate control valve 111 that controls the flow rate of the refrigerant liquid pipe 108. The flow control valve 111 is composed of, for example, an electronic expansion valve. The refrigeration cycle apparatus 100 further includes an oil separator 112 that separates oil from the refrigerant discharged from the screw compressor 102, and an oil supply pipe 113 that supplies the oil separated by the oil separator 112 to the screw compressor 102. It has. Here, the oil separator 112 is introduced separately from the compressor. However, the oil separator 112 may have an oil separator integrated type in which the function of the oil separator is provided in the compressor.

The screw compressor 102 sucks a refrigerant and compresses the refrigerant to a high temperature and high pressure state. The screw compressor 102 is driven by power being supplied from a power supply source (not shown) to the motor 103 via the inverter 101.

The condenser 104 cools and condenses the refrigerant gas discharged from the screw compressor 102. The main expansion valve 105 squeezes and expands the refrigerant liquid that passes through the refrigerant liquid pipe 109, and is composed of an electronic expansion valve. The main expansion valve 105 constitutes a main pressure reducing device according to the present invention. In addition to the electronic decompression device, the main decompression device may be a mechanical expansion valve, a temperature expansion valve, a capillary tube, or any other type as long as it plays a similar role. . The evaporator 106 evaporates the refrigerant that has flowed out of the main expansion valve 105.

A suction gas temperature sensor 120 that detects the temperature of the suction gas sucked into the screw compressor 102 is provided on the suction side of the screw compressor 102. The suction temperature detected by the suction gas temperature sensor is output to the control device 110 described later.

The refrigeration cycle apparatus 100 further includes a control device 110. The control device 110 performs overall control of the refrigeration cycle apparatus 100, such as opening control of the main expansion valve 105, position control of a slide valve described later, and opening control of the flow control valve 111. As the opening degree control of the main expansion valve 105, the control device 110 controls the main expansion valve 105 so that the suction SH becomes a target value during steady operation. Here, the steady operation refers to an operation excluding the unsteady operation, and the unsteady operation refers to, for example, when the degree of superheat of the suction gas (hereinafter referred to as suction SH) suddenly increases, such as at the start of operation, It refers to driving that is higher than suction SH.

Further, the control device 110 controls the flow rate control valve 111 according to the discharge temperature as the opening degree control of the flow rate control valve 111. Specifically, the flow control valve 111 is controlled so that the discharge temperature is within a preset setting range. 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 screw compressor 102 sucks and compresses refrigerant gas, which is a gaseous refrigerant, and then discharges it. The discharge gas discharged from the screw compressor 102 flows into the oil separator 112. In the oil separator 112, the refrigerant and the oil mixed in the refrigerant are separated, and the refrigerant is cooled by the condenser 104. The refrigerant cooled by the condenser 104 is branched after passing through the condenser 104, and the mainstream refrigerant is decompressed by the main expansion valve 105 and expanded. Then, the refrigerant flowing out from the main expansion valve 105 is heated by the evaporator 106 and becomes refrigerant gas. The refrigerant gas flowing out of the evaporator 106 is sucked into the screw compressor 102.

On the other hand, of the refrigerant liquid after passing through the condenser 104, the refrigerant branched from the mainstream refrigerant flows into the refrigerant liquid pipe 108. Then, the refrigerant liquid is injected into the compression chamber 5 by the differential pressure between the pressure of the refrigerant liquid in the refrigerant liquid pipe 108 and the pressure in the compression chamber of the screw compressor 102. The injected refrigerant liquid is mixed with the refrigerant gas being compressed, compressed, and discharged from the screw compressor 102.

Also, the oil discharged together with the refrigerant from the screw compressor 102 is separated from the refrigerant by the oil separator 112 and returned to the screw compressor 102 through the oil supply pipe 113. As described above, the oil is returned to the screw compressor 102 so that the oil is not exhausted in the screw compressor 102.

(Screw compressor)
Hereinafter, the screw compressor 102 according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram of the screw compressor according to Embodiment 1 of the present invention. FIG. 3 is a development view of the outer peripheral surface of the screw rotor of the screw compressor according to Embodiment 1 of the present invention, and the position of the screw groove and the injection port when the slide valve is disposed at the first position on the discharge side. It is a figure which shows a relationship. FIG. 4 is a development view of the outer periphery of the screw rotor of the screw compressor according to the first embodiment of the present invention, and the positions of the screw groove and the injection port when the slide valve is arranged at the second position on the suction side. It is a figure which shows a relationship.

2, the screw compressor 102 includes a casing 1, a screw rotor 3, a gate rotor 6, a motor 103 that rotationally drives the screw rotor 3, a slide valve 7, and the like. The casing 1 accommodates the screw rotor 3, the gate rotor 6, the motor 103, the slide valve 7, and the like.

In the casing 1, a cylindrical housing wall 1a that forms a substantially cylindrical space is formed, and a substantially columnar screw rotor 3 is disposed inside the housing wall 1a. 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. In addition, a rotating shaft 4 is provided integrally with the center of the screw rotor 3. The rotating shaft 4 is rotatably supported by a bearing 2 provided in the casing 1.

Further, for example, a motor 103 whose frequency is controlled by an inverter 101 is connected to the end of the rotating shaft 4 on the side opposite to the bearing 2. The motor 103 includes a stator 103a that is inscribed and fixed to the casing 1, and a motor rotor 103b that is disposed inside the stator 103a. And the rotating shaft 4 is connected with the motor rotor 103b, and the screw rotor 3 is rotationally driven.

The gate rotor 6 has a disk shape, and a plurality of teeth 6a to be engaged with the screw grooves 3a are formed on the outer periphery. A space surrounded by the teeth 6 a of the gate rotor 6, the screw grooves 3 a and the housing wall 1 a of the casing 1 becomes the compression chamber 5.

Further, the casing 1 has a partition wall (not shown) in which a low-pressure gas refrigerant is introduced from the evaporator 106 of the refrigerant circuit, and a high-pressure gas refrigerant discharged from the compression chamber 5 flows into the casing 1. It is divided into and. A discharge port (see FIG. 5 described later) 10 that opens to a discharge chamber (not shown) is formed on the high pressure side in the casing 1.

Further, the casing 1 is formed with an oil injection port 114 for supplying the oil separated by the oil separator 112 to the screw groove 3a. As shown in FIGS. 3 and 4, the oil injection port 114 is formed at a position facing the screw groove 3 a between immediately before and after the start of compression. Although the oil injection port 114 is provided in the casing 1, it may be provided in a slide valve for capacity control described later or a slide valve having a variable internal volume ratio. Furthermore, an oil injection port may be provided on both the casing and the slide valve for controlling the capacity or having a variable internal volume ratio.

Further, as shown in FIG. 2, a slide groove 1 b extending in the direction of the rotating shaft 4 of the screw rotor 3 is formed on the inner peripheral surface 1 aa side of the housing wall 1 a of the casing 1. A slide valve 7 for changing the liquid injection position is accommodated in the slide groove 1b so as to be slidable in the direction of the rotating shaft 4. The slide valve 7 forms part of the inner peripheral surface 1aa together with the casing 1 in order to close the opening of the screw groove 3a to form the compression chamber 5. FIG. 2 shows a configuration in which one slide valve 7 for changing the liquid injection position is provided in the casing 1. In addition, a slide valve for capacity control or a slide valve having a variable internal volume ratio is further provided. May be. 3 and 4 show an example in which a slide valve 11 for changing the internal volume is provided.

The slide valve 7 changes the injection position of the refrigerant liquid into the screw groove 3a constituting the compression chamber 5, and the refrigerant liquid injection flow path 7a for injecting the refrigerant liquid from the outside into the screw groove 3a is formed through. Has been. The refrigerant liquid injection flow path 7a is provided on the surface side of the slide valve 7 facing the housing wall 1a of the casing 1, and is provided in communication with the liquid groove 7aa having a long groove shape extending in the sliding direction and the liquid groove 7aa. And a cylindrical injection port 7ab that opens to the screw rotor 3 side.

The slide valve 7 is configured to be movable between a first position on the discharge side (see FIG. 3) and a second position on the suction side (see FIG. 4). By moving to the first position on the discharge side, The injection timing can be delayed, and the injection timing can be advanced by moving to the second position on the suction side.

The position of the injection port 7ab in the state where the slide valve 7 is located at the first position is the position on the suction side of the casing 1 when the slide valve 7 and the casing 1 are viewed in plan view from the outside as shown in FIG. The position is on the discharge side (left side in FIG. 3) along the end face 1d. Therefore, the position of the injection port 7ab in the state where the slide valve 7 is located at the first position can be said to be a position facing the screw groove 3a from immediately before the start of compression to immediately after the compression. Therefore, in a state where the slide valve 7 is located at the first position, liquid injection of the refrigerant liquid into the screw groove 3a is started immediately before and after the start of compression.

Further, the position of the injection port 7ab in a state where the slide valve 7 is located at the second position on the suction side is a position facing the screw groove 3ab before the compression starts, that is, the suction stroke, as shown in FIG. Therefore, in a state where the slide valve 7 is positioned at the second position, the refrigerant liquid is injected into the screw groove 3a before the compression starts. In addition, when the refrigerant liquid is injected into the screw groove 3a in the suction stroke, if it is performed in the first half of the suction stroke, the suction of the suction gas into the compression chamber 5 is inhibited. For this reason, it is preferable to inject the refrigerant liquid into the screw groove 3a in the suction stroke in the latter half of the suction stroke.

As described above, the position of the injection port 7ab in the state where the slide valve 7 is located at the first position and the position of the oil injection port 114 are both “screw groove 3a between immediately before and after the start of compression. The position in the circumferential direction is different. That is, the slide valve 7 is provided on the side opposite to the rotational direction of the screw rotor 3 with respect to the oil injection port 114 as shown in FIG. Therefore, the injection port 7ab and the oil injection port 114 in a state where the slide valve 7 is positioned at the first position are different in the position in the direction of the rotation shaft 4 (the position in the left-right direction in FIG. 3). Is located on the suction side (right side of FIG. 3). Therefore, when the slide valve 7 is positioned at the second position on the suction side, the position of the injection port 7ab in the direction of the rotation shaft 4 is greater than that when the slide valve 7 is positioned at the first position on the discharge side. It approaches the port 114.

The slide valve 7 is connected to a drive device 9 such as a piston via a connecting rod 8, and can be moved in the slide groove 1 b to the first position and the second position by the drive of the drive device 9. . Here, the driving device 9 is not limited to a driving method using a motor or the like separately from a piston driven by a gas pressure, a hydraulic drive, or a piston.

Further, as shown in FIG. 2, the casing 1 is formed with a refrigerant liquid flow path 1c that communicates the outside of the casing 1 and the slide groove 1b. The refrigerant liquid flow path 1c has an opening on the slide groove 1b side of the refrigerant liquid flow path 1c in the liquid storage groove 7aa provided in the slide valve 7 regardless of whether the slide valve 7 is positioned at the first position or the second position. The positional relationship with the slide valve 7 is set so as to communicate. A refrigerant liquid pipe 108 (see FIG. 1) is connected to the opening of the refrigerant liquid flow path 1c on the casing outer side.

With this configuration, regardless of whether the slide valve 7 is positioned at the first position or the second position, the refrigerant liquid branched from between the condenser 104 and the main expansion valve 105 is transferred to the refrigerant liquid pipe 108, the refrigerant liquid. It flows into the screw groove 3a constituting the compression chamber 5 through the flow path 1c and the refrigerant liquid injection flow path 7a.

Here, the refrigerant used in the refrigerant circuit is not particularly limited. For example, an HFC refrigerant such as R134a or an HFO refrigerant that is a low GWP refrigerant is used as the refrigerant.

(Description of operation)
Next, the operation of the screw compressor in the first embodiment will be described.

FIG. 5 is a diagram illustrating a compression principle of the screw compressor according to Embodiment 1 of the present invention.
As shown in FIG. 5, the screw rotor 3 is rotated by the motor 103 (see FIG. 2) via the rotating shaft 4 (see FIG. 1), so that the teeth 6a of the gate rotor 6 are relatively moved in the screw groove 3a. Move to. As a result, in the compression chamber 5, the suction stroke, the compression stroke, and the discharge stroke are set as one cycle, and this cycle is repeated. In FIG. 5, the part enclosed by the dotted line shows the accommodating wall 1a of the casing 1, and the compression chamber 5 constituted by the screw groove 3a located in the region surrounded by the accommodating wall 1a is in the compression stroke. Here, focusing on the compression chamber 5 indicated by hatching of dots in FIG. 5, each stroke will be described.

5A, screw grooves 3ac and 3ad are in the compression stroke, screw grooves 3aa and 3ab are in the suction stroke, and 3ae is in the discharge stroke. When the screw rotor 3 is driven by the motor 103 and rotates in the direction of the solid arrow from the state of FIG. 5A, the lower gate rotor 6 shown in FIG. Rotate to. Further, the upper gate rotor 6 shown in FIG. 5 rotates in the opposite direction to the lower gate rotor 6 as indicated by a hollow arrow. In the suction stroke, the compression chamber 5 has the most expanded volume, communicates with the low pressure space of the casing 1, and is filled with low pressure refrigerant gas.

When the screw rotor 3 further rotates, the teeth 6a of the two gate rotors 6 sequentially rotate toward the discharge port 10 in conjunction with the rotation. As a result, the volume (volume) of the compression chamber 5 is reduced as shown in FIG.

When the screw rotor 3 continues to rotate, the compression chamber 5 communicates with the discharge port 10 as shown in FIG. Thereby, the high-pressure refrigerant gas compressed in the compression chamber 5 is discharged to the outside from the discharge port 10. Then, the same compression is performed again on the back surface of the screw rotor 3.

In FIG. 5, the slide groove 1b and the refrigerant liquid injection flow path 7a of the slide valve 7 are not shown, but in the compression stroke, the refrigerant liquid flows into the screw groove 3a from the refrigerant liquid injection flow path 7a and is compressed. The refrigerant gas in the chamber 5 is cooled, compressed together with the suction gas, and discharged outside in the discharge stroke. In FIG. 5, the oil injection port 114 is not shown, but the oil separated by the oil separator 112 is supplied from the oil injection port 114 to the screw groove 3a.

In the screw compressor configured as described above, refrigerant liquid injection (hereinafter sometimes referred to as liquid injection) for the purpose of suppressing an increase in discharge temperature is performed during steady operation. The liquid injection at the time of steady operation starts in the compression chamber 5 immediately before and after the completion of the suction of the suction gas. Thereby, the inconvenience that the refrigerant liquid leaks to the suction side and the suction of the suction gas into the compression chamber 5 is hindered can be prevented.

And in this Embodiment 1, as mentioned above, liquid injection was performed at the time of steady operation, and it became possible to suppress seizure of the screw rotor 3 at the time of unsteady operation, suppressing an increase in discharge temperature. It is characterized by that.

In order to suppress seizure of the screw rotor 3 during unsteady operation, the positions of the liquid injection port and the oil injection port 114 in the direction of the rotation shaft 4 (positions in the left and right directions in FIGS. 3 and 4) are close to each other. It is valid. The high temperature oil separated by the oil separator 112 during the unsteady operation is supplied from the oil injection port 114 to the screw groove 3a. At that time, since the screw rotor 3 is rotating, oil is supplied to a circumferential region of the screw rotor 3 including a portion where the oil injection port 114 is located in a position of the screw rotor 3 in the direction of the rotation axis 4. It will be. For this reason, this peripheral area | region among the outer peripheral surfaces of the screw rotor 3 is easy to expand especially with a temperature rise.

Therefore, by performing liquid injection in this circumferential region, it is possible to concentrate and cool the high temperature portion, and to suppress the thermal expansion of the screw rotor 3 and to suppress the seizure of the screw rotor 3. It becomes possible. In order to perform liquid injection in the circumferential region, the position of the injection port 7ab in the direction of the rotation axis 4 should be close to the oil injection port 114.

As described above, the injection position is required to be different between the steady operation and the unsteady operation, and this is realized by the movement of the slide valve 7. Specifically, the slide valve 7 is moved to the first position on the discharge side during steady operation, and the slide valve 7 is moved to the second position on the suction side during non-steady operation. Note that it is possible to determine whether the current operation state is a steady operation state or an unsteady operation state based on the suction SH. That is, it can be determined that the steady operation is performed when the suction SH is low, and the unsteady operation is performed when the suction SH is high.

Hereinafter, the liquid injection control for moving the slide valve 7 will be described with reference to the flowchart of FIG.

FIG. 6 is a view showing a flowchart of liquid injection control in the refrigeration cycle apparatus including the screw compressor according to Embodiment 1 of the present invention. In addition, the flow control valve 111 shall open to the initial opening degree at the time of an operation start.

The control device 110 (see FIG. 1) calculates the actual suction SH based on the suction gas temperature detected by the suction gas temperature sensor 120. Then, if the measured suction SH is not less than the set suction SH_A and not more than the set suction SH_B (step S1; Yes), that is, if in the steady operation state, the control device 110 discharges the slide valve 7 as shown in FIG. The first position is moved to the first position (step S2). The set suction SH_A and the set suction SH_B are set in the control device 110 in advance. The set suction SH_A and the set suction SH_B are threshold values for determining whether the operation is a steady operation or an unsteady operation. That is, if the measured suction SH is less than the set suction SH_A, the liquid back operation (unsteady operation) is performed, and if the measured suction SH is larger than the set suction SH_B, the suction SH raising operation (unsteady operation) is performed. In the liquid back operation, the gasified refrigerant is normally sucked into the compressor, but the liquid and gas are mixed and sucked into the compressor. Then, by moving the slide valve 7 to the first position, the injection port 7ab moves to a position facing the screw groove 3ac between immediately before and after the start of compression.

Subsequently, the control device 110 controls the flow rate control valve 111 according to the actually measured discharge temperature detected by a discharge temperature sensor (not shown). Specifically, if the measured discharge temperature is higher than the first preset temperature set in advance (Step S3; No), the opening degree of the flow control valve 111 is increased (Step S4), and the measured discharge temperature is set to the first setting. If the temperature is lower than the second set temperature lower than the temperature (step S5; No), the opening degree of the flow control valve 111 is decreased (step S6). On the other hand, if the measured discharge temperature is not lower than the second set temperature and not higher than the first set temperature (step S3; Yes, step S5; Yes), the current opening degree is maintained.

On the other hand, if the determination in step S1 is No and the actually measured suction SH is larger than the set suction SH_B (step S7; Yes), that is, in the unsteady operation state, the control device 110 slides as shown in FIG. The valve 7 is moved to the second position on the suction side (step S8). Accordingly, as described above, the position of the injection port 7ab in the direction of the rotation axis 4 can be brought close to the oil injection port 114, and the screw rotor 3 can be effectively cooled. Further, since liquid injection is performed on the screw groove 3ab before the start of compression, that is, the screw groove 3ab in the suction stroke, it also contributes to a decrease in the measured suction SH. In this way, the measured suction SH decreases by performing liquid injection on the screw groove 3ab in the suction stroke.

Then, in order to reduce the suction SH, the opening of the main expansion valve 105 is increased (step S9). If the measured discharge temperature is higher than the first set temperature (step S10; No), the opening degree of the flow control valve 111 is increased (step S11), and the process returns to step S9 to increase the opening degree of the main expansion valve 105. Repeat the operation. On the other hand, if the actually measured discharge temperature is equal to or lower than the first set temperature (step S10; Yes), the opening degree of the flow control valve 111 is reduced (step S12), and the process returns to step S1 to check the decrease state of the actually measured suction SH. .

Further, when the actual suction SH is not greater than or equal to the set suction SH_A and less than or equal to the set suction SH_B, and the actual suction SH is not greater than the set suction SH_B (step S1; No, step S7; No), that is, the actual suction SH is the set suction. When it is less than SH_A, it is determined as a liquid back operation (unsteady operation). When determining that the liquid back operation (unsteady operation) is performed, the control device 110 moves the slide valve 7 to the first position on the discharge side (step S13), and then increases the suction SH to increase the suction SH. The opening is reduced (step S14). Thereby, it switches to the state where liquid injection is started immediately before and after the start of compression. The subsequent operation is as described above.

As described above, according to the first embodiment, since the slide valve 7 for moving the injection port 7ab according to the suction SH is provided, the injection position of the liquid injection is changed between the steady operation and the unsteady operation. Can do. Therefore, at the time of steady operation, the liquid injection is started immediately before and after the start of the compression, so that the liquid refrigerant leaks to the suction side, and the discharge of the suction gas into the compression chamber 5 is not hindered. An increase in temperature can be suppressed.

In addition, during non-steady operation, liquid injection can be performed in a circumferential region where thermal expansion is likely to occur due to oil supply from the oil injection port 114, and quality defects such as seizure between the screw rotor 3 and the casing 1 can occur. Can be suppressed. Moreover, at the time of unsteady driving | operation, the raise of suction | inhalation SH can be suppressed by liquid-injecting into the screw groove | channel 3a in a suction stroke.

Further, since the flow rate of the liquid injection can be adjusted according to the discharge temperature by the flow rate control valve 111, it is possible to suppress an increase in the discharge temperature with an optimal liquid injection amount. Therefore, since the inhibition of the refrigerant suction into the compression chamber 5 can be minimized, the influence on the performance degradation can be reduced.

Embodiment 2. FIG.
In the second embodiment, in addition to the configuration of the first embodiment, an on-off valve 107 for opening and closing the flow path of the refrigerant liquid pipe 108 is provided in the refrigerant liquid pipe 108. The on-off valve 107 is composed of, for example, an electromagnetic valve. In the second embodiment, differences from the first embodiment will be described, and configurations not described in the first embodiment are the same as those in the first embodiment.

FIG. 7 is a refrigerant circuit diagram of the refrigeration cycle apparatus according to Embodiment 2 of the present invention.
The refrigeration cycle apparatus 100 of the second embodiment has a configuration in which an on-off valve 107 is further provided in the refrigerant liquid pipe 108 of the first embodiment shown in FIG. The expansion valve constituting the flow control valve 111 is generally not guaranteed to completely close the flow path. For this reason, the flow path of the refrigerant liquid pipe 108 cannot be completely closed only by providing the flow rate control valve 111 in the refrigerant liquid pipe 108. Therefore, even if the flow control valve 111 is closed when it is not necessary to perform the liquid injection, the liquid injection is slightly performed. Therefore, by providing the on-off valve 107, it is possible to completely close the flow path of the refrigerant liquid pipe 108 and stop the liquid injection.

In the second embodiment, the same effects as in the first embodiment can be obtained, and the on / off valve 107 is provided in the refrigerant liquid pipe 108, so that the following effects are further obtained. That is, in the operation region where the discharge temperature is difficult to rise, the liquid injection can be stopped by closing the on-off valve 107. Therefore, it is possible to prevent the performance degradation due to the intermediate pressure rise due to the liquid injection being performed at an originally unnecessary timing.

In the first and second embodiments, the screw compressor 102 is a single screw compressor. However, the present invention can be applied to other twin screw compressors, for example. Furthermore, the present invention can be applied to a specification having an economizer as a configuration of the refrigeration cycle.

1 casing, 1a containing wall, 1aa inner peripheral surface, 1b slide groove, 1c refrigerant liquid flow path, 1d end surface, 2 bearing, 3 screw rotor, 3a screw groove, 3aa screw groove, 3ab screw groove, 3ac screw groove, 3ad screw Groove, 3ae screw groove, 4 rotary shaft, 5 compression chamber, 6 gate rotor, 6a tooth, 7 slide valve, 7a refrigerant liquid injection channel, 7aa liquid reservoir groove, 7ab injection port, 8 connecting rod, 9 drive unit, 10 Discharge port, 11 slide valve, 100 refrigeration cycle device, 101 inverter, 102 screw compressor, 103 motor, 103a stator, 103b motor rotor, 104 condenser, 105 main expansion valve, 106 evaporator, 107 on-off valve, 10 Refrigerant liquid pipe, 109 a refrigerant liquid pipe, 110 controller, 111 a flow control valve, 112 an oil separator, 113 an oil supply pipe, 114 oil injection port 120 suction gas temperature sensor.

Claims

A casing in which a refrigerant liquid passage through which refrigerant liquid from the outside passes is formed;
A plurality of screw grooves forming a compression chamber are formed on the outer peripheral surface, and a screw rotor arranged to rotate in the casing;
A slide valve that is provided between the casing and the screw rotor and slides in the direction of the rotation axis of the screw rotor;
The casing or the slide valve or both are provided with an oil injection port for supplying oil to the screw groove,
The slide valve has a refrigerant liquid injection channel that communicates the refrigerant liquid channel with the screw groove, and the slide valve communicates with the screw groove between immediately before and after the start of compression. 1 position and a position where the refrigerant liquid injection flow path communicates with the screw groove in the suction stroke before the start of compression, and the position in the rotational axis direction is closer to the oil injection port than the first position. Screw compressor moving to the second position.
2. The screw compressor according to claim 1, wherein the position of the slide valve is switched to the first position or the second position in accordance with the suction superheat degree of the suction gas.
The refrigerant liquid injection channel includes a liquid reservoir groove that communicates with the refrigerant liquid channel regardless of whether the slide valve is located at the first position or the second position, and an injection port that communicates with the liquid reservoir groove. The screw compressor of Claim 1 or Claim 2 which has these.
A refrigeration cycle apparatus comprising a refrigerant circuit in which the screw compressor, the condenser, the main decompression device, and the evaporator according to any one of claims 1 to 3 are connected in order.
A refrigerant liquid pipe branched from between the condenser and the main decompressor and connected to the refrigerant liquid flow path of the screw compressor;
A flow rate control valve that is provided in the refrigerant liquid piping and controls a flow rate of the refrigerant flowing through the refrigerant liquid piping;
An oil separator for separating oil from the refrigerant discharged from the screw compressor;
An oil supply pipe for supplying oil separated by the oil separator to the oil injection port of the screw compressor;
5. The refrigeration cycle apparatus according to claim 4, further comprising: a control device that moves the slide valve to the first position or the second position based on a suction superheat degree of the refrigerant sucked into the screw compressor.
The control device moves the slide valve to the first position when the suction superheat degree is equal to or lower than a preset suction superheat degree, and when the suction superheat degree is larger than the set suction superheat degree, The refrigeration cycle apparatus according to claim 5, wherein the slide valve is moved to the second position.
The refrigeration cycle apparatus according to claim 5 or 6, wherein the control device controls the flow rate control valve so that a discharge temperature of refrigerant discharged from the screw compressor is within a preset setting range.
The refrigeration cycle apparatus according to any one of claims 5 to 7, further comprising an on-off valve that opens and closes a flow path of the refrigerant liquid pipe.