Screw compressor and refrigeration cycle device

Abstract

The present invention provides a screw compressor to be used in an economizer cycle in which a refrigerant is injected into a compression chamber during a compression stage. The screw compressor comprises: a compression unit which has a screw shaft serving as a rotary shaft and which compresses the refrigerant; a casing that accommodates the compression unit and forms a compression chamber together with the compression unit; and a valve that allows the refrigerant to pass through in one direction. At least one economizer flow channel is formed inside the casing, said channel being used for injection of the refrigerant and connecting the outside of the casing with the compression chamber. A valve that prevents backflow of the refrigerant is disposed in each of the at least one economizer flow channel.

Description

Screw compressor and refrigeration cycle device

[0001] The present disclosure relates to a screw compressor and a refrigeration cycle device equipped with an economizer function.

[0002] Conventionally, refrigeration systems operate at rated conditions for a very short period of time throughout the year, with over 90% of the yearly operating time being at partial load. Partial load operation, particularly at 75-50% of full load, accounts for the majority of such operations. The refrigerant circulation flow rate and operating compression ratio differ between full load operation and partial load operation, and the coefficient of performance also changes. Taking these actual operating conditions into consideration, the seasonal coefficient of performance has been gaining attention. In other words, the seasonal coefficient of performance is an index that emphasizes the coefficient of performance under partial load conditions. The coefficient of performance is the ratio of refrigeration capacity to compressor input, and is the coefficient of performance of a refrigeration system throughout a period of time.

[0003] In refrigeration systems equipped with a compressor that operates using a refrigerant, factors such as the seasonal coefficient of performance that takes into account performance during partial load operation have become increasingly important due to growing environmental awareness, and performance improvements during partial load operation are being sought. Therefore, in order to increase the coefficient of performance of the refrigeration cycle, a refrigeration cycle system has been proposed that includes an economizer in the refrigeration cycle and performs economizer operation by sending economizer gas from the economizer to a compression chamber (see, for example, Patent Document 1). The refrigeration cycle system of Patent Document 1 includes a check valve installed in a piping section connecting the economizer and the screw compressor to suppress the effect of pressure pulsations generated within the screw compressor on the piping connecting the economizer and the screw compressor.

[0004] Japanese Patent Application Laid-Open No. 60-134166

[0005] The refrigeration cycle apparatus of Patent Document 1 includes a check valve installed in a pipe connecting an economizer and a screw compressor. Specifically, the refrigeration cycle apparatus of Patent Document 1 includes a check valve installed in an economizer pipe that forms a flow path between the economizer and the screw compressor. Therefore, the refrigeration cycle apparatus of Patent Document 1 may encounter the following problem when a small amount of refrigerant is supplied to the economizer flow path under operating conditions with a low compression ratio, or when the economizer flow path is closed. In the refrigeration cycle apparatus of Patent Document 1, compressed refrigerant may backflow into the economizer piping flow path from the compression chamber to the check valve. As the screw rotor continues to rotate and the economizer port connects to the next compression chamber (screw tooth groove), the compressed refrigerant that has backflowed into the economizer piping flow path may return to the compression chamber. Furthermore, in the refrigeration cycle apparatus of Patent Document 1, as the screw rotor continues to rotate and the pressure in the compression chamber increases, the compressed refrigerant may again backflow from the compression chamber into the economizer piping flow path. The economizer piping has a dead volume where the refrigerant gas is wasted from the suction pressure to the discharge pressure. Therefore, the refrigeration cycle device of Patent Document 1 may experience power loss due to recompression of the refrigerant gas flowing from the compression chamber into the economizer piping or compression of the dead volume.

[0006] The present disclosure has been made in consideration of the above points, and an object of the present disclosure is to provide a screw compressor and a refrigeration cycle device that reduce power loss and have high performance particularly during partial load operation, even under low compression ratio conditions with a low economizer flow rate or when the economizer flow path is closed.

[0007] The screw compressor according to the present disclosure is a screw compressor used in an economizer cycle in which a refrigerant is injected into a compression chamber during a compression process, and is equipped with a compression section having a screw shaft as a rotating shaft and compressing the refrigerant, a casing that houses the compression section and defines the compression chamber together with the compression section, and a valve that allows the refrigerant to pass in one direction, and inside the casing is formed at least one economizer flow path that is a flow path used for injecting the refrigerant and that connects the outside of the casing with the compression chamber, and a valve is disposed in each of the at least one economizer flow path to prevent backflow of the refrigerant.

[0008] A refrigeration cycle apparatus according to the present disclosure includes the screw compressor configured as described above, a condenser that condenses a refrigerant, an expansion valve that decompresses the refrigerant flowing therein, an economizer having a high-pressure section through which the refrigerant flowing from the condenser flows and a low-pressure section into which the refrigerant flowing from the high-pressure section flows and is disposed between the condenser and the expansion valve, an evaporator that evaporates the refrigerant, an economizer expansion valve that decompresses the refrigerant flowing out from the high-pressure section of the economizer and causes the refrigerant flowing out from the high-pressure section to flow into the low-pressure section of the economizer, a refrigerant piping that configures a refrigerant circuit that sequentially connects the screw compressor, the condenser, the high-pressure section of the economizer, the expansion valve, and the evaporator, and an economizer piping that branches off between the economizer and the expansion valve and configures a branch circuit that is connected to an economizer flowpath of the screw compressor via the economizer expansion valve and the low-pressure section of the economizer.

[0009] According to the present disclosure, a screw compressor has at least one economizer flow path formed inside a casing, the economizer flow path being a flow path used for injecting refrigerant and connecting the outside of the casing with a compression chamber, and each of the at least one economizer flow paths is provided with a valve for preventing backflow of refrigerant. By providing a valve for preventing backflow of refrigerant in the economizer flow path inside the casing, the screw compressor can reduce refrigerant that flows back from the compression chamber to the economizer piping outside the casing even when the amount of refrigerant supplied to the economizer flow path is small or when the economizer flow path is closed, thereby reducing dead volume loss. Therefore, the screw compressor can reduce power loss even under low compression ratio conditions with a low economizer flow rate or when the economizer flow path is closed, and can improve performance, particularly during partial load operation.

[0010] 1. A refrigerant circuit diagram of a refrigeration cycle apparatus including a screw compressor according to embodiment 1. A cross-sectional schematic diagram of the screw compressor according to embodiment 1. A conceptual diagram of a cross section of the screw compressor according to embodiment 1 taken along line A-A, as viewed in the direction of the arrows. A schematic cross-sectional diagram of the screw compressor according to embodiment 1 taken along the screw shaft. An enlarged schematic diagram of part A in FIG. 4 of the screw compressor according to embodiment 1. A plan view of the valve according to embodiment 1 taken from direction B in FIG. 5. A plan view of another aspect of the valve according to embodiment 1 taken from direction B in FIG. 5. A conceptual diagram showing a state of the valve of the screw compressor according to embodiment 1 when the refrigerant flows normally through the economizer flow path. A conceptual diagram showing a state of the valve of the screw compressor according to embodiment 1 when the refrigerant flows backward through the economizer flow path. A schematic cross-sectional schematic diagram of a screw compressor according to embodiment 2 taken along the screw shaft. An enlarged schematic diagram of part C in FIG. 10 of the screw compressor according to embodiment 2. A perspective view of a housing of the valve according to embodiment 2. 1 is a conceptual diagram showing a state of refrigerant flowing when the flow of refrigerant in the economizer passage is normal in the screw compressor according to embodiment 2. FIG. 2 is a conceptual diagram showing a state of a valve in a valve of the screw compressor according to embodiment 2 when the flow of refrigerant in the economizer passage is normal. FIG. 3 is a conceptual diagram showing a state of a valve in a valve of the screw compressor according to embodiment 2 when the flow of refrigerant in the economizer passage is reverse. FIG. 4 is a schematic diagram showing an end face portion on the high-pressure side of a casing in a screw compressor according to embodiment 3. FIG. 5 is a schematic diagram of a cross section taken along the screw shaft of the screw compressor according to embodiment 3. FIG. 6 is a side view of a bearing housing of the screw compressor according to embodiment 3. FIG. 7 is a schematic diagram of a cross section taken along the screw shaft of another example of the screw compressor according to embodiment 3.

[0011] Embodiments of a screw compressor and a refrigeration cycle apparatus according to the present disclosure will be described below with reference to the drawings. Note that in the following drawings, including FIG. 1 , the relative dimensional relationships and shapes of the components may differ from those in reality. In the following drawings, identical reference numerals denote identical or equivalent components, and this applies throughout the entire specification. To facilitate understanding, directional terms (e.g., up, down, right, left, front, rear, etc.) are used as appropriate. However, these notations are merely used for the sake of convenience and do not limit the arrangement or orientation of the apparatus or components. Note that the present disclosure is not limited by these embodiments. The shapes, sizes, arrangements, etc. of the components shown in the drawings may be changed as appropriate within the scope of the present disclosure.

[0012] Embodiment 1 [Refrigeration cycle apparatus 200] Fig. 1 is a refrigerant circuit diagram of a refrigeration cycle apparatus 200 including a screw compressor 100 according to Embodiment 1. The refrigeration cycle apparatus 200 is used for various purposes, such as an air conditioner, a refrigeration apparatus, and a hot water supply apparatus.

[0013] The refrigeration cycle apparatus 200 includes a screw compressor 100, a condenser 102 that condenses a refrigerant, an expansion valve 104 that decompresses the refrigerant flowing therethrough, and an evaporator 105 that evaporates the refrigerant. The refrigeration cycle apparatus 200 also includes an economizer 103 that has a high-pressure section 103a through which the refrigerant flowing out of the condenser 102 flows and a low-pressure section 103b into which the refrigerant flowing out of the high-pressure section 103a flows, and is disposed between the condenser 102 and the expansion valve 104. The refrigeration cycle apparatus 200 also includes an economizer expansion valve 106 that decompresses the refrigerant flowing out of the high-pressure section 103a of the economizer 103 and causes the refrigerant to flow into the low-pressure section 103b of the economizer 103.

[0014] The refrigeration cycle apparatus 200 also includes a refrigerant pipe 201 that configures a refrigerant circuit 202 that sequentially connects the screw compressor 100, the condenser 102, the high-pressure section 103a of the economizer 103, the expansion valve 104, and the evaporator 105. The refrigeration cycle apparatus 200 also configures a branch circuit 203 that branches off between the economizer 103 and the expansion valve 104 and is connected to an economizer flow path 15 of the screw compressor 100 that is provided with a valve 50 (described later) via an economizer expansion valve 106 and a low-pressure section 103b of the economizer 103. The refrigeration cycle apparatus 200 also includes an economizer pipe 107 that configures the branch circuit 203.

[0015] The refrigerant circuit 202 and the branch circuit 203 configure an economizer cycle in which refrigerant is injected from the intercooler 103 into the compression chamber 11 (see FIG. 3 described later) during the compression process. In the refrigeration cycle apparatus 200, the intercooler 103 exchanges heat between the refrigerant in the refrigerant circuit 202 and the refrigerant flowing through the branch circuit 203 through the economizer cycle, thereby subcooling the refrigerant flowing to the expansion valve 104, and returning the refrigerant flowing to the economizer pipe 107 to the screw compressor 100. The refrigerant returned to the screw compressor 100 is in a gas state or a gas-liquid two-phase state depending on the control.

[0016] The screw compressor 100 draws in a low-temperature, low-pressure refrigerant, compresses the drawn refrigerant, and discharges a high-temperature, high-pressure refrigerant. The screw compressor 100 is equipped with an inverter device 101, and controls the capacity, which is the amount of refrigerant delivered per unit time, by changing the operating frequency.

[0017] The condenser 102 cools and condenses the refrigerant gas that has been discharged from the screw compressor 100 and flowed into the condenser 102. The expansion valve 104 throttles and expands the refrigerant that has flowed out from the intercooler 103 and flowed into the expansion valve 104. The expansion valve 104 reduces the pressure of the refrigerant flowing inside the expansion valve 104. The expansion valve 104 is, for example, a pressure reducer that performs expansion electrically. The evaporator 105 evaporates the refrigerant that has flowed out from the expansion valve 104 and flowed into the evaporator 105.

[0018] The intercooler 103 cools the high-pressure side refrigerant by performing heat exchange between the high-pressure side refrigerant between the condenser 102 and the expansion valve 104 and a low-pressure side refrigerant obtained by reducing the pressure of a portion of the high-pressure side refrigerant by an intercooler expansion valve 106. The intercooler 103 performs heat exchange between the refrigerant flowing through the refrigerant circuit 202 and the refrigerant flowing through the branch circuit 203.

[0019] The economizer expansion valve 106 throttles and expands the refrigerant that flows out from the high-pressure section 103a of the economizer 103 and flows into the economizer expansion valve 106. The economizer expansion valve 106 reduces the pressure of the refrigerant flowing inside the economizer expansion valve 106. The economizer expansion valve 106 is, for example, a pressure reducer that performs expansion or the like electrically.

[0020] The refrigeration cycle apparatus 200 further includes a control device 210 that controls the inverter device 101, the expansion valve 104, and the intercooler expansion valve 106. The control device 210 also controls the entire refrigeration cycle apparatus 200, such as controlling the position of the slide valve 12 (see FIG. 3 described later) of the screw compressor 100 and starting and stopping the economizer operation. The economizer operation is an operation in which an intercooler 103 is provided in the refrigeration cycle and economizer gas from the intercooler 103 is sent to the compression chamber 11 for the purpose of increasing the coefficient of performance of the refrigeration cycle.

[0021] [Configuration of screw compressor 100] Fig. 2 is a cross-sectional schematic diagram of the screw compressor 100 according to embodiment 1. Fig. 3 is a conceptual diagram of a cross section of the screw compressor 100 according to embodiment 1 taken along line A-A, as viewed in the direction of the arrows. The basic configuration of the screw compressor 100 will be described with reference to Figs. 2 and 3.

[0022] The screw compressor 100 according to the first embodiment is a compressor used in an economizer cycle in which a refrigerant is injected into a compression chamber 11 during a compression process. The screw compressor 100 is a rotary positive displacement compressor. Although a single screw compressor is illustrated as the screw compressor 100 in FIGS. 2 and 3 , the screw compressor 100 is not limited to a single screw compressor and may be another type of screw compressor, such as a twin screw compressor.

[0023] The screw compressor 100 includes a cylindrical casing 1, a screw rotor 4, a gate rotor 7, a slide valve 12, an electric motor 8 that rotates and drives the screw rotor 4, and a valve 50. The screw compressor 100 includes at least a compression section 20, which will be described later, the casing 1, and the valve 50.

[0024] The casing 1 houses the compression section 20 and, together with the compression section 20, defines a compression chamber 11. More specifically, the casing 1 houses the screw rotor 4, the gate rotor 7, the electric motor 8, the slide valve 12, etc. The interior of the casing 1 has a housing section 1A that forms a substantially cylindrical space, and the substantially cylindrical screw rotor 4 is housed inside the housing section 1A. The casing 1 is formed with a discharge port 18 that opens into the housing section 1A.

[0025] The screw rotor 4 is cylindrical, and a plurality of screw grooves 10 extending helically from one end to the other end of the screw rotor 4 are formed on the outer circumferential surface. The portion on one end of the screw rotor 4 forms the refrigerant gas suction side, and the screw grooves 10 communicate with a space on the suction pressure side. The portion on the other end of the screw rotor 4 forms the refrigerant gas discharge side, and the screw grooves 10 communicate with a space on the discharge pressure side. The screw rotor 4 is mounted on the outer circumferential surface of a screw shaft 9. The screw shaft 9, which serves as a drive shaft, is integrally formed at the center of the screw rotor 4.

[0026] The screw shaft 9 is rotatably supported by a high-pressure side bearing 2 and a low-pressure side bearing 3 provided in the casing 1. An electric motor 8, the frequency of which is controlled by, for example, an inverter (not shown), is connected to the end of the screw shaft 9 on the low-pressure side bearing 3 side. The screw shaft 9 is driven to rotate by the electric motor 8. The screw shaft 9 also serves as the drive shaft of the electric motor 8.

[0027] The high-pressure side bearing 2 and the low-pressure side bearing 3 provided in the casing 1 are formed in a cylindrical shape, and when viewed in the axial direction of the screw shaft 9, they are formed in an annular shape. The high-pressure side bearing 2 has an end of the screw shaft 9 disposed therein and rotatably supports the end of the screw shaft 9. The low-pressure side bearing 3 has the screw shaft 9 disposed therein and rotatably supports the screw shaft 9. In FIG. 2, the low-pressure side bearing 3 is provided in approximately the center of the screw shaft 9 in the axial direction, but it may also be provided to support the end of the screw shaft 9 located opposite the high-pressure side bearing 2.

[0028] The high-pressure side bearing 2 is accommodated in a bearing housing 30. The bearing housing 30 is formed in a cylindrical shape. The bearing housing 30 is located inside the casing 1 on the opposite side from the electric motor 8, at the end of the high-pressure side.

[0029] A pair of gate rotor support chambers 6 are formed in the casing 1 so as to face each other with the accommodation portion 1A at the center. In other words, a pair of gate rotor support chambers 6 are formed in the casing 1 so as to face each other with the screw rotor 4 at the center. A substantially disk-shaped gate rotor 7 is accommodated in each of the pair of gate rotor support chambers 6. The gate rotor 7 is provided on a gate rotor support 5 accommodated in the gate rotor support chamber 6.

[0030] The gate rotor support 5 is disposed so that its central axis 5b, which serves as the rotation axis, is approximately perpendicular to the screw shaft 9 of the screw rotor 4. The gate rotor support 5 is rotatably supported by bearings 5a disposed opposite to and spaced apart in the axial direction of the central axis 5b.

[0031] As shown in Fig. 3, a gate rotor 7 and a gate rotor support 5 are housed in the respective spaces of a gate rotor support chamber 6 formed on the left side of the housing section 1A and a gate rotor support chamber 6 formed on the right side of the housing section 1A. The gate rotors 7 and gate rotor supports 5 housed in the left and right gate rotor support chambers 6 are arranged rotated 180° around the screw shaft 9 of the screw rotor 4. In other words, a pair of gate rotors 7 are arranged on the side surfaces of the screw rotor 4. The pair of gate rotors 7 are arranged so as to be axially symmetrical with respect to the screw shaft 9.

[0032] The gate rotor 7, together with the accommodation portion 1A and the screw rotor 4, forms a compression chamber 11. The gate rotor 7 is formed in a disk shape, and a plurality of teeth 7a are formed on its outer periphery along the circumferential direction to mesh with the screw grooves 10. The teeth 7a of the gate rotor 7 are arranged to mesh with the screw grooves 10 of the screw rotor 4.

[0033] A gate rotor opening 1a into which the teeth 7a are inserted is formed in the casing 1. The gate rotor opening 1a is formed to extend in the axial direction of the screw shaft 9. The gate rotor opening 1a is formed to extend along the inclination of the screw groove 10 on the back surface, and is formed to be connected to the suction wall (not shown) of the accommodation section 1A that forms the compression chamber 11 on the back surface.

[0034] The outer periphery of the gate rotor 7 is inserted into a gate rotor opening 1a provided in the casing 1. That is, the teeth 7a of the gate rotor 7 are inserted into the accommodation portion 1A through the gate rotor opening 1a and mesh with the screw grooves 10. As a result, in the screw compressor 100, a space is formed that is surrounded by the gate rotor 7, the inner wall surface of the accommodation portion 1A, and the screw rotor 4, and this space serves as a compression chamber 11. That is, in the screw compressor 100, the space that is surrounded by the teeth 7a of the gate rotor 7 and the screw grooves 10 partitioned by the accommodation portion 1A serves as the compression chamber 11. Alternatively, when the slide valve 12 is also taken into consideration, in the screw compressor 100, the compression chamber 11 that compresses the refrigerant is formed by the space that is surrounded by the screw grooves 10, the teeth 7a, the inner circumferential surface of the casing 1, and the slide valve 12.

[0035] At least the screw rotor 4, gate rotor 7, and screw shaft 9 constitute a compression section 20 that compresses and discharges the drawn refrigerant. The compression section 20 has the screw shaft 9 as a rotation shaft and compresses the refrigerant. The compression section 20 also includes a screw rotor 4 that is provided along the outer periphery of the screw shaft 9, is rotatably housed inside the housing section 1A of the casing 1, and has a plurality of screw grooves 10 provided on its outer periphery. The compression section 20 also includes a gate rotor 7 that has teeth 7a that mesh with the plurality of screw grooves 10 provided on its outer periphery and forms a compression chamber 11 together with the plurality of screw grooves 10 and the housing section 1A.

[0036] Two slide grooves 14 extending in the axial direction of the screw shaft 9 of the screw rotor 4 are formed on the inner wall surface of the casing 1, and a slide valve 12 is housed inside the slide grooves 14 so that it can slide freely. The slide valve 12 is disposed between the inner surface of the casing 1 and the screw rotor 4. Each of the two slide grooves 14 is formed in a substantially cylindrical shape, and a portion of the inner circumferential surface communicates with the housing portion 1A. These two slide grooves 14 are arranged rotated 180° around the screw shaft 9 of the screw rotor 4.

[0037] The slide valve 12 provided in the slide groove 14 is formed in a substantially cylindrical shape, similar to the slide groove 14. The slide valve 12 is formed in a shape in which a portion of the cylinder is cut out so that the opposing surface 1e that faces the accommodation portion 1A conforms to the outer peripheral wall of the accommodation portion 1A. The slide valve 12 is provided along the outer peripheral surface of the screw rotor 4. The slide valve 12 is provided so as to be slidable in the axial direction of the screw rotor 4.

[0038] The slide valve 12 is connected to a drive device (not shown) via a coupling part (not shown), and by driving the linear actuator, the slide valve 12 moves inside the slide groove 14 in the axial direction of the screw shaft 9 of the screw rotor 4. The slide valve 12 may be used for mechanical capacity control, or may be used for changing the internal volume by changing the timing of discharge.

[0039] The electric motor 8 drives the compression section 20 that compresses the refrigerant. The electric motor 8 has a stator 8a that is fixed in contact with the interior of the casing 1 and a rotor 8b that is arranged inside the stator 8a. The rotor 8b is fixed to a screw shaft 9 that is the driving rotation shaft of the compression section 20 and is arranged on the same line as the screw rotor 4. The electric motor 8 is inverter-driven and its rotation speed can be changed by inverter driving. The electric motor 8 may also be a constant-speed motor that rotates at a constant rotation speed.

[0040] Fig. 4 is a schematic cross-sectional view taken along the screw shaft 9 of the screw compressor 100 according to the first embodiment. Fig. 5 is an enlarged schematic view of part A in Fig. 4 of the screw compressor 100 according to the first embodiment. The valve mechanism outside the casing 1 shown in Fig. 4 may or may not be included. The valve 50 and the economizer flow path 15 of the casing 1 in which the valve 50 is provided will be described using Figs. 3 to 5.

[0041] At least one economizer flow path 15, which is a flow path used for injecting a refrigerant and which connects the outside of the casing 1 with the compression chamber 11, is formed inside the casing 1. The screw compressor 100 is provided with the economizer flow path 15 in the casing 1 for guiding the refrigerant flowing out from the economizer 103 to the compression chamber 11. In other words, the screw compressor 100 is provided with the economizer flow path 15 in the casing 1 for guiding the refrigerant flowing out from the economizer 103 to the screw grooves 10 in the compression process. In the refrigeration cycle apparatus 200, an economizer pipe 107 is connected to the economizer flow path 15, and the economizer 103 and the economizer flow path 15 are connected to each other.

[0042] The economizer flow path 15 formed in the casing 1 is a part or the whole of the economizer flow path 15 formed in the screw compressor 100. A part of the economizer flow path 15 may be formed by another member, such as a bearing housing 30 attached to the casing 1 (see FIG. 16 ).

[0043] The economizer flow passage 15 according to the first embodiment forms a flow passage from the outer peripheral surface 1b of the cylindrical casing 1 to the compression chamber 11 inside the casing 1. Fig. 3 shows an embodiment in which two economizer flow passages 15 are formed in the casing 1. The number of economizer flow passages 15 is not limited to two, and may be one, or three or more. That is, the number of economizer flow passages 15 may be one or more.

[0044] As shown in Fig. 3 , each of the at least one economizer flow passages 15 is formed in the casing 1 and extends so as to communicate between the outside of the casing 1 and the compression chamber 11 when the casing 1 is viewed in the axial direction of the screw shaft 9. For example, each of the at least one economizer flow passages 15 extends in a radial direction perpendicular to the screw shaft 9 when the casing 1 is viewed in the axial direction of the screw shaft 9. Also, as shown in Fig. 4 , each of the at least one economizer flow passages 15 is formed in the casing 1 and extends on an imaginary axis that intersects with the screw shaft 9 when viewed in a direction perpendicular to the axial direction of the screw shaft 9. In Fig. 4 , an axis CA indicates the imaginary axis that intersects with the screw shaft 9 when viewed in a direction perpendicular to the axial direction of the screw shaft 9.

[0045] The economizer flow path 15 according to the first embodiment is formed in a straight line. However, the economizer flow path 15 is not limited to being formed in a straight line, and may include a curved portion.

[0046] At least one economizer flow path 15 is provided with a valve 50 that prevents refrigerant from flowing back from the compression chamber 11 to the outside of the casing 1. The valve 50 allows refrigerant flowing through the flow path to pass in one direction. The casing 1 is formed with an economizer port 16 as an open end of the economizer flow path 15 on the compression chamber 11 side. The casing 1 is formed with an open end 17 as an open end of the economizer flow path 15 on the opposite side from the compression chamber 11 side. It is desirable to position the valve 50 closer to the economizer port 16 than the open end 17 on the outer peripheral surface 1b side of the casing 1. The open end 17 and the economizer pipe 107 are connected, for example, by a nipple (not shown).

[0047] Note that the term "backflow of the refrigerant" used in the description of the embodiment refers to the direction in which the refrigerant flows in the opposite direction to the forward flow, where the direction in which the refrigerant flows through the economizer flow path 15 during economizer operation is defined as the forward flow of the refrigerant. In other words, the direction in the economizer flow path 15 in which the refrigerant flows from the compression chamber 11 to the outside of the casing 1 is referred to as the backflow of the refrigerant.

[0048] 5 , at least one economizer flow passage 15 has a step 19 formed therein, where the opening diameter decreases in the direction from the outside of the casing 1 toward the compression chamber 11. The step 19 is preferably formed closer to the economizer port 16 than to the opening end 17 on the outer circumferential surface 1 b side of the casing 1. That is, the step 19 is preferably formed closer to the economizer port 16 than to the opening end 17 in the economizer flow passage 15. The end of the valve 50 on the compression chamber 11 side is located at the step 19.

[0049] The valve 50 may be any valve having a check function. The valve 50 allows refrigerant to pass from the outside of the casing 1 toward the compression chamber 11, but blocks refrigerant from passing from the compression chamber 11 to the outside of the casing 1. The valve 50 is, for example, a check valve, which allows refrigerant to pass from the outside of the casing 1 into the compression chamber 11, but prevents refrigerant from flowing out of the casing 1 from the compression chamber 11.

[0050] Figure 6 is a plan view of the valve 50 according to embodiment 1, as seen from direction B in Figure 5. Figure 7 is a plan view of another aspect of the valve 50 according to embodiment 1, as seen from direction B in Figure 5. In Figures 6 and 7, the positions of a valve body 52 and a central through-hole 51e, which will be described later, are indicated by dotted lines. The configuration of the valve 50 according to embodiment 1 will be further described using Figures 5 to 7.

[0051] The valve 50 is formed in a cylindrical shape and has a housing 51 in which a support portion 51c, which is one end, is positioned in the stepped portion 19, and a valve seat portion 51b, which is the other end, is fixed to the economizer flow path 15 by a retaining ring 54. The valve 50 also has a valve element 52 that is movably disposed inside the housing 51 and moves due to the pressure of the refrigerant. The valve 50 has the housing 51 with the valve element 52 built in seated on the stepped portion 19, and the surface opposite the stepped portion 19 is fixed by the retaining ring 54. The retaining ring 54 is made of, for example, metal, but is not limited to, a metal material.

[0052] The housing 51 is made of, for example, metal, but may be made of other materials such as resin. As shown in Fig. 5, the housing 51 has a cylindrical portion 51a that forms a cylindrical shape. The housing 51 also has a support portion 51c that forms one end surface of the cylindrical portion 51a on the economizer port 16 side, and a valve seat portion 51b that forms the other end surface of the cylindrical portion 51a opposite the support portion 51c.

[0053] The support portion 51c is formed in a disk shape. As shown in Figures 6 and 7, a first through hole 51d1 is formed in the support portion 51c, and a valve body lower portion 52b of the valve body 52 described below is inserted into the first through hole 51d1. The support portion 51c slidably supports the valve body lower portion 52b inserted into the first through hole 51d1. A plurality of second through holes 51d2 are formed in the support portion 51c on the outer periphery of the first through hole 51d1.

[0054] The plurality of second through holes 51d2 are holes through which the refrigerant passes. Although the number of second through holes 51d2 is three in FIG. 6 and four in FIG. 7, any number of second through holes 51d2 may be used. As shown in FIGS. 6 and 7, the plurality of second through holes 51d2 are formed on the outer periphery side of the first through holes 51d1 when viewed in the axial direction of the valve body 52. ​​The plurality of second through holes 51d2 are formed at intervals in the circumferential direction. In other words, the support portion 51c extends to connect the central portion and the outer periphery side portion.

[0055] When viewed in the axial direction of the valve body 52, the support portion 51c has an annular central portion 51c1, an annular outer peripheral portion 51c2, and bridging portions 51c3 that connect the central portion 51c1 and the outer peripheral portion 51c2 and are formed radially from the central portion 51c1. When viewed in the axial direction of the valve body 52, a first through hole 51d1 is formed at the center of the central portion 51c1, and second through holes 51d2 are formed between adjacent bridging portions 51c3 in the circumferential direction.

[0056] The valve seat 51b is formed in a disk shape. As shown in Figure 5, a central through-hole 51e is formed in the center of the valve seat 51b. The central through-hole 51e is a hole through which the refrigerant passes. When the valve 50 is closed, the valve element 52 is seated on the valve seat 51b and closes the central through-hole 51e. The central through-hole 51e and the second through-hole 51d2 form part of the economizer flow path 15.

[0057] The valve element 52 is formed in a cylindrical shape and has a valve element lower part 52b that is inserted into the support part 51c and movably supported by the support part 51c. The valve element 52 is also formed in a cylindrical shape with a larger diameter than the valve element lower part 52b and has a valve element upper part 52a that seats on the valve seat part 51b to stop the flow of refrigerant when the valve 50 is closed and seats on the support part 51c to allow the refrigerant to pass when the valve 50 is open. The valve element 52 moves due to the pressure of the refrigerant.

[0058] As shown in FIGS. 6 and 7, when viewed in the axial direction of the valve body 52, the valve body upper portion 52a covers only a portion of the second through-hole 51d2.

[0059] The valve 50 is formed so that the valve body upper portion 52a is located closer to the center than the outermost portion of the second through-hole 51d2 when viewed in the axial direction of the valve body 52. ​​When the valve body upper portion 52a is seated on the support portion 51c while the valve 50 is open, the valve body upper portion 52a does not cover the entire second through-hole 51d2, and the valve 50 has a portion through which the refrigerant passes.

[0060] Fig. 8 is a conceptual diagram showing the state of the valve 50 of the screw compressor 100 according to embodiment 1 when the refrigerant flows normally through the economizer flow path 15. Fig. 9 is a conceptual diagram showing the state of the valve 50 of the screw compressor 100 according to embodiment 1 when the refrigerant flows backward through the economizer flow path 15. The solid arrows shown in Figs. 8 and 9 indicate the flow of refrigerant.

[0061] As shown in Fig. 8, in the normal flow of refrigerant through the economizer flow passage 15, the refrigerant flows from the open end 17 (see Fig. 4) of the economizer flow passage 15 toward the economizer port 16. The flow of refrigerant from the open end 17 (see Fig. 4) toward the economizer port 16 presses the valve disc 52 against the support portion 51c and seats it there. The refrigerant passes through the central through-hole 51e of the valve seat portion 51b, between the valve disc upper portion 52a of the valve disc 52 and the cylindrical portion 51a of the housing 51, and through the second through-hole 51d2 of the support portion 51c, passes through the valve 50, and flows from the open end 17 toward the compression chamber 11. When the valve disc 52 seats on the support portion 51c, the economizer flow passage 15 of the screw compressor 100 is opened.

[0062] As shown in Figure 9, when the refrigerant flowing through the economizer flow passage 15 is reverse, the refrigerant flows from the economizer port 16 of the economizer flow passage 15 toward the open end 17 (see Figure 4). When the refrigerant flowing through the economizer flow passage 15 is reverse, the valve disc 52 is pressed against the valve seat 51b by the refrigerant flowing back from the compression chamber 11. When the valve 50 is closed, the valve disc upper part 52a seats on the valve seat 51b, blocking the central through-hole 51e and stopping the flow of refrigerant. In the screw compressor 100, as shown in the area surrounded by dashed line D, when the valve disc 52 seats on the valve seat 51b, the central through-hole 51e is blocked by the valve disc upper part 52a of the valve disc 52, and the economizer flow passage 15 is closed.

[0063] [Explanation of Operation of Refrigeration Cycle Apparatus 200] Next, operation of the refrigeration cycle apparatus 200 will be described with reference to Fig. 1. First, an example of operation during full load operation will be described. The low-pressure gas refrigerant that has discharged from the evaporator 105 is sucked into the screw compressor 100, compressed, and then discharged. The discharged refrigerant is subcooled in the condenser 102. The high-pressure subcooled liquid enters the high-pressure section 103a of the economizer 103 and is further cooled. A portion of the high-pressure liquid that has discharged from the economizer 103 is branched, throttled and expanded to an intermediate pressure by the economizer expansion valve 106, and flows again into the low-pressure section 103b of the economizer 103.

[0064] The high-pressure liquid (high-pressure side refrigerant) that leaves the condenser 102 and directly flows into the high-pressure section 103a of the economizer 103 increases in degree of subcooling due to heat exchange with the refrigerant liquid (low-pressure side refrigerant) that passes through the economizer expansion valve 106 and flows again into the low-pressure section 103b of the economizer 103. That is, in the refrigeration cycle apparatus 200, the refrigeration effect of the evaporator 105 increases due to this increase in subcooling.

[0065] Meanwhile, the refrigerant liquid (low-pressure side refrigerant) that has flowed back into the low-pressure section 103b of the economizer 103 evaporates through heat exchange with the high-pressure side refrigerant and becomes refrigerant gas. This refrigerant gas then passes through the economizer pipe 107 and the economizer flow path 15, is injected into the screw groove 10 of the compression chamber 11 that is being compressed, and is mixed with the compressed gas.

[0066] At this time, the compression power of the refrigeration cycle device 200 changes depending on the amount and timing of gas inflow into the screw compressor 100. Therefore, the key to increasing the coefficient of performance is to increase the refrigeration capacity without increasing the compression power as much as possible.

[0067] Next, an example of operation when the high-low differential pressure is small during partial load operation will be described. When the high-low differential pressure is small during partial load operation, the difference between the intermediate pressure (the pressure at the outlet of the economizer 103) and the pressure in the compression chamber 11 when the economizer gas flows in is small. This may cause the intermediate pressure to transiently become lower than the pressure in the compression chamber 11 during economizer operation, resulting in unstable operation of the refrigeration cycle apparatus 200. Furthermore, the refrigeration cycle apparatus 200 may have a small effect on increasing its refrigeration capacity, and the increase in power due to the inflow of the economizer gas during compression may be greater. Therefore, under conditions where the high-low differential pressure is small, the refrigeration cycle apparatus 200 may close the economizer expansion valve 106 to prevent economizer operation. Furthermore, the economizer expansion valve 106 may be closed for economizer flow rate control (e.g., economizer outlet superheat).

[0068] [Operation and Effect of the Screw Compressor 100] The screw compressor 100 has at least one economizer flow path 15 formed inside the casing 1. The economizer flow path 15 is a flow path used for injecting a refrigerant and connects the outside of the casing 1 with the compression chamber 11. The screw compressor 100 has a valve 50 disposed in each of the at least one economizer flow path 15 to prevent backflow of the refrigerant. The screw compressor 100 has the valve 50 disposed in the economizer flow path 15 inside the casing 1 to prevent backflow of the refrigerant. With this configuration, the screw compressor 100 can reduce the amount of refrigerant that flows back from the compression chamber 11 to the economizer pipe 107 outside the casing 1, thereby reducing dead volume loss, even in the following cases. Note that the following cases include, for example, when the amount of refrigerant supplied to the economizer flow path is small or when the economizer flow path is closed. Therefore, the screw compressor 100 can reduce power loss even under low compression ratio conditions with a low economizer flow rate or when the economizer flow path is closed, thereby improving performance particularly during partial load operation. Note that the "dead volume loss" refers collectively to the backflow of compressed refrigerant into the dead volume, and the refrigerant that has flowed into the dead volume and then flows back into the compression chamber 11 and is recompressed. Note that the dead volume is a volume portion that is wastedly compressed between the suction pressure and the discharge pressure.

[0069] In a refrigeration cycle equipped with a screw compressor 100 having an economizer cycle, the amount of refrigerant supplied to the economizer pipe 107 decreases under operating conditions with a low compression ratio, and the refrigeration cycle apparatus 200 may close the flow path depending on the control. The refrigeration cycle apparatus 200 has a valve 50 installed in the economizer flow path 15 inside the screw compressor 100, particularly near the economizer port 16. With the above configuration, the refrigeration cycle apparatus 200 can reduce dead volume loss and improve performance, particularly during partial load operation, by suppressing backflow of compressed refrigerant into the economizer pipe 107 even in the following cases. Examples of such cases include when the amount of refrigerant supplied to the economizer flow path is small or when the economizer flow path is closed.

[0070] The casing 1 also has a housing portion 1A in which a discharge port is formed and which forms a cylindrical space. The compression section 20 includes a screw rotor 4 provided along the outer periphery of the screw shaft 9, which is rotatably housed inside the housing portion 1A of the casing 1 and has a plurality of screw grooves 10 formed on its outer periphery. The compression section 20 also includes a gate rotor 7, which has teeth 7a formed on its outer periphery that mesh with the plurality of screw grooves 10 and which forms a compression chamber 11 together with the screw grooves 10 and the housing portion 1A. The screw compressor 100 has the above-described configuration and is a single-screw compressor. Even when used as a single-screw compressor, the screw compressor 100 can reduce power loss even under low compression ratio conditions with a low economizer flow rate or when the economizer flow path is closed, thereby improving performance, particularly during partial load operation.

[0071] Furthermore, each of the at least one economizer flow passages 15 is formed in the casing 1 and extends so as to communicate between the outside of the casing 1 and the compression chamber 11 when the casing 1 is viewed in the axial direction of the screw shaft 9. Furthermore, each of the at least one economizer flow passages 15 is formed in the casing 1 and extends on a virtual axis that intersects with the screw shaft 9 when viewed in a direction perpendicular to the axial direction of the screw shaft 9. Since the economizer flow passage 15 is configured as described above, it can be formed by machining a through-hole from the outside of the casing 1 toward the compression chamber 11, which makes it easy to process and form.

[0072] Furthermore, the valve 50 is a check valve that allows refrigerant flowing into the compression chambers 11 from outside the casing 1 to pass through and prevents refrigerant from flowing out of the casing 1 from the compression chambers 11. By providing the valve 50, which is a check valve, in the economizer flow path 15 in the screw compressor 100, even when the economizer flow path is closed, the amount of refrigerant that flows back from the compression chambers 11 to the economizer pipe 107 outside the casing 1 can be reduced, thereby reducing dead volume loss. Therefore, the screw compressor 100 can reduce power loss even under low compression ratio conditions with a low economizer flow rate or when the economizer flow path is closed, and can improve performance, particularly during partial load operation.

[0073] Each of at least one economizer passage 15 has a stepped portion 19 where the opening diameter decreases in a direction from the outside of the casing 1 toward the compression chamber 11. The valve 50 has a cylindrical housing 51. A support portion 51c, which is one end of the housing 51, is located at the stepped portion 19, and a valve seat portion 51b, which is the other end of the housing 51, is fixed to the economizer passage 15 by a retaining ring 54. The valve 50 also has a valve disc 52 that is movably located inside the housing 51 and moves due to the pressure of the refrigerant. The valve disc 52 is cylindrical and has a valve disc lower portion 52b that is inserted into and movably supported by the support portion 51c. The valve disc 52 is cylindrical and has a diameter larger than that of the valve disc lower portion 52b. The valve disc 52 has a valve disc upper portion 52a that seats on the valve seat portion 51b to stop the flow of refrigerant when the valve 50 is closed and seats on the support portion 51c to allow the refrigerant to pass when the valve 50 is open.

[0074] By providing the valve 50 having the above configuration in the economizer flow path 15, the screw compressor 100 can reduce the amount of refrigerant that flows back from the compression chamber 11 to the economizer pipe 107 outside the casing 1, even when the economizer flow path is closed, thereby reducing dead volume loss. Therefore, the screw compressor 100 can reduce power loss even under low compression ratio conditions with a low economizer flow rate, or when the economizer flow path is closed, and can improve performance particularly during partial load operation.

[0075] The refrigeration cycle apparatus 200 also includes a screw compressor 100, a condenser 102 that condenses a refrigerant, and an expansion valve 104 that decompresses the refrigerant flowing therethrough. The refrigeration cycle apparatus 200 also includes a high-pressure section 103a through which the refrigerant flowing out from the condenser 102 flows, and a low-pressure section 103b into which the refrigerant flowing out from the high-pressure section 103a flows, and an economizer 103 that is disposed between the condenser 102 and the expansion valve 104. The refrigeration cycle apparatus 200 also includes an evaporator 105 that evaporates the refrigerant, and an economizer expansion valve 106 that decompresses the refrigerant flowing out from the high-pressure section 103a of the economizer 103 and causes the refrigerant to flow into the low-pressure section 103b of the economizer 103. The refrigeration cycle apparatus 200 also includes refrigerant piping 201 that configures a refrigerant circuit 202 that sequentially connects the screw compressor 100, the condenser 102, the high-pressure section 103a of the economizer 103, the expansion valve 104, and the evaporator 105. The refrigeration cycle apparatus 200 also configures a branch circuit 203 that branches off between the economizer 103 and the expansion valve 104 and is connected to the economizer flow path 15 of the screw compressor 100 via the economizer expansion valve 106 and the low-pressure section 103b of the economizer 103. The refrigeration cycle apparatus 200 includes an economizer piping 107 that configures the branch circuit 203.

[0076] The refrigeration cycle device 200 includes the screw compressor 100, and therefore can achieve the same effects as the screw compressor 100.

[0077] Embodiment 2. Fig. 10 is a schematic cross-sectional view taken along the screw shaft 9 of a screw compressor 100 according to embodiment 2. Fig. 11 is an enlarged schematic view of part C in Fig. 10 of the screw compressor 100 according to embodiment 2. Embodiment 2 differs from embodiment 1 in the configurations of the valve 50A and the economizer flow path 15. The other configurations are the same as or equivalent to those of embodiment 1. The following description will focus on the configurations in embodiment 2 that differ from embodiment 1, and configurations not described in embodiment 2 are the same as those of embodiment 1. The valve 50A and the economizer flow path 15 of the casing 1 in which the valve 50A is provided will be described using Figs. 10 and 11 .

[0078] The casing 1 is formed with at least one economizer flow path 15, which is a flow path used for injecting a refrigerant and which connects the outside of the casing 1 with the compression chambers 11. The economizer flow path 15 forms a flow path from the end face side of the cylindrical casing 1 to the compression chambers 11 inside the casing 1. As described above, there may be one or more economizer flow paths 15.

[0079] 10 and 11 , each of the at least one economizer passage 15 is formed in an upside-down L-shape when viewed in a direction perpendicular to the axial direction of the screw shaft 9. Note that the economizer passage 15 is indicated by a dashed line in Fig. 10 and 11 . The economizer passage 15 extends from the compression chamber 11 toward the outer peripheral surface 1b of the casing 1 and also extends along the screw shaft 9 toward the high-pressure side end face of the casing 1.

[0080] The economizer flow path 15 includes a part of the first flow path 15a and a second flow path 15b. The economizer flow path 15 is formed, for example, so as to bend at a right angle by the first flow path 15a and the second flow path 15b. The first flow path 15a extends on an imaginary axis that intersects with the screw shaft 9 when viewed in a direction perpendicular to the axial direction of the screw shaft 9. In Fig. 10, an axis CA indicates the imaginary axis that intersects with the screw shaft 9 when viewed in a direction perpendicular to the axial direction of the screw shaft 9.

[0081] Furthermore, the first flow passage 15a is formed in the casing 1, and when the casing 1 is viewed in the axial direction of the screw shaft 9, the first flow passage 15a extends so as to communicate between the outside of the casing 1 and the compression chamber 11. For example, when the casing 1 is viewed in the axial direction of the screw shaft 9, the first flow passage 15a extends in a radial direction perpendicular to the screw shaft 9. One end of the first flow passage 15a, an economizer port 16, communicates with the compression chamber 11, and the other end opposite the compression chamber 11, an outer peripheral end 15a1, is blocked by a blocking member 15a2 such as a plug.

[0082] The first flow path 15a is formed, for example, by machining a through hole from the outside of the casing 1, and an outer peripheral end 15a1 is closed with a blocking member 15a2 such as a plug. The second flow path 15b is formed, for example, by machining a hole from the high-pressure side end face of the casing 1, and drilling the hole deeper than the first flow path 15a. Then, the housing 51A is installed inside the second flow path 15b.

[0083] The second flow passage 15b is formed in the casing 1 and extends along the axial direction of the screw shaft 9. One end of the second flow passage 15b, an inner end 15b1 on the compression chamber 11 side, crosses and communicates with the first flow passage 15a, while the other end, an outer end 15b2 on the opposite side of the compression chamber 11, communicates with the outside of the casing 1. As shown in FIG. 10 , the inner end 15b1 is the end on the side where the electric motor 8 is located, and the other end, the outer end 15b2, is the end on the side where the electric motor 8 is not located. A connection flange 25 is provided at one end of the casing 1. The connection flange 25 is located on the high-pressure side of the casing 1 and serves as a lid for forming a discharge flow passage or an oil flow passage. The connection flange 25 may include a slide valve control mechanism. In this embodiment, the outer end 15b2 of the second flow passage 15b communicates with the outside of the casing 1.

[0084] A valve 50A that prevents backflow of refrigerant is disposed in each of at least one economizer flow paths 15. The valve 50A allows refrigerant flowing through the flow path to pass in one direction. The valve 50A is disposed at the intersection of the first flow path 15a and the second flow path 15b. The valve 50A is, for example, a housing 51A that houses a valve element 52 and a spring 55 and is installed at the point where the first flow path 15a and the second flow path 15b intersect at a right angle, and is fixed in place with a retaining ring 54.

[0085] The valve 50A is disposed along the second flow path 15b so as to bridge between the opposing inner walls of the first flow path 15a in the radial direction when viewed in the axial direction of the first flow path 15a. In other words, the valve 50A is disposed so as to intersect with the first flow path 15a and close the first flow path 15a.

[0086] Figure 12 is a perspective view of a housing 51A of a valve 50A according to embodiment 2. The configuration of the valve 50A according to embodiment 2 will be further described with reference to Figures 11 and 12. The valve 50A allows refrigerant to pass from the outside of the casing 1 toward the compression chamber 11, but blocks refrigerant from passing from the compression chamber 11 to the outside of the casing 1.

[0087] The valve 50A has a cylindrical housing 51A with a valve seat 51b formed at one end. The valve 50A is disposed within the housing 51A so as to be movable along the axial direction of the housing 51A, and has a cylindrical valve element 52 that seats on the valve seat 51b to stop the flow of refrigerant when the valve 50A is closed, and moves away from the valve seat 51b to allow the refrigerant to pass when the valve 50A is open. The valve 50A also has a spring 55 disposed within the housing 51A to bias the valve element 52 toward the valve seat 51b.

[0088] 11 and 12 , the housing 51A has a tubular portion 51a1 that forms a cylindrical portion and a valve seat 51b that forms one end surface of the tubular portion 51a1. The housing 51A is disposed in the second flow path 15b, and the valve seat 51b is disposed closer to the end surface 1f (see FIG. 10 ) on the high-pressure side of the casing 1 than the first flow path 15a. The housing 51A is disposed so that the valve seat 51b is located on the outer end 15b2 side that is the other end of the second flow path 15b, rather than on the inner end 15b1 side that is one end of the second flow path 15b.

[0089] The cylindrical portion 51a1 is formed in a cylindrical shape. A side opening 51f, which is a through-hole communicating with the first flow path 15a, is formed on the outer peripheral surface of the cylindrical portion 51a1 of the housing 51A. The side opening 51f is a hole through which the refrigerant passes. The side opening 51f opens toward the compression chamber 11 and forms a flow path leading to the economizer port 16.

[0090] The valve seat 51b is formed in a circular plate shape. An end surface opening 51e1, which is a through-hole, is formed in the center of the valve seat 51b. In other words, the end surface opening 51e1 is formed in the end surface of the housing 51A. The end surface opening 51e1 is a through-hole that communicates with the second flow path 15b and whose periphery forms the valve seat 51b. The end surface opening 51e1 is a hole through which the refrigerant passes. When the valve 50A is closed, the valve element 52 seats on the valve seat 51b and closes the end surface opening 51e1. The side surface opening 51f and the end surface opening 51e1 form part of the economizer flow path 15.

[0091] The valve element 52 is formed in a cylindrical shape. Note that the term "cylindrical shape" also includes a disk-like shape. The valve element 52 is disposed within the cylindrical portion 51a1 of the housing 51A. The valve element 52 is disposed so as to be freely movable along the axial direction of the housing 51A. The valve element 52 moves due to the pressure of the refrigerant and the biasing force of the spring 55. When the valve 50A is closed, the valve element 52 seats on the valve seat portion 51b to stop the flow of the refrigerant, and when the valve 50A is open, the valve element 52 leaves the valve seat portion 51b to allow the refrigerant to pass through.

[0092] As described above, the spring 55 is disposed inside the housing 51A and biases the valve element 52 toward the valve seat 51b. The spring 55 is a cylindrical coil spring, one end of which abuts against the inner end 15b1 of the second flow path 15b and the other end of which abuts against the valve element 52. The spring 55 biases the valve element 52 in the direction that closes the end surface opening 51e1, pressing the valve element 52 against the valve seat 51b.

[0093] Fig. 13 is a conceptual diagram showing a state of refrigerant flowing in the screw compressor 100 according to the second embodiment when the refrigerant flows normally in the economizer passage 15. Fig. 14 is a conceptual diagram showing a state of the valve 50A of the screw compressor 100 according to the second embodiment when the refrigerant flows normally in the economizer passage 15. Fig. 15 is a conceptual diagram showing a state of the valve 50A of the screw compressor 100 according to the second embodiment when the refrigerant flows backward in the economizer passage 15. Note that the solid arrows in Figs. 13 to 15 indicate the refrigerant flow.

[0094] As shown in Fig. 13 , when the refrigerant flows normally through the economizer flow path 15, the refrigerant flows from the outside of the end face side of the casing 1 toward the economizer port 16. The refrigerant presses against a first surface 52c of the valve element 52, which is the surface facing the valve seat 51b. A second surface 52d of the valve element 52, which is the surface opposite to the first surface 52c, is pressed by a spring 55. As shown in Fig. 14 , when the pressure of the refrigerant flowing toward the economizer port 16 exceeds the biasing force of the spring 55, the valve element 52 moves away from the valve seat 51b and moves toward the inner end 15b1 of the second flow path 15b.

[0095] When the valve disc 52 moves a predetermined distance away from the valve seat 51b, the end face opening 51e1, the interior of the housing 51, and the side face opening 51f are in communication with each other at the valve 50A of the screw compressor 100. Also, when the valve disc 52 moves a predetermined distance away from the valve seat 51b, the first flow path 15a and the second flow path 15b are in communication with each other in the economizer flow path 15 of the screw compressor 100, and the economizer flow path 15 is opened. More specifically, the screw compressor 100 has the first flow path 15a and the second flow path 15b in communication with each other via the end face opening 51e1, the interior of the housing 51, and the side face opening 51f, and the economizer flow path 15 is opened.

[0096] 14 , in the screw compressor 100, when the valve 50A is opened in the economizer passage 15, the second passage 15b communicates with the portion of the first passage 15a between the valve 50A and the compression chamber 11. The refrigerant flows through the second passage 15b, the end surface opening 51e1, the interior of the housing 51, the side surface opening 51f, and the portion of the first passage 15a between the valve 50A and the compression chamber 11, and then flows into the compression chamber 11.

[0097] 15 , when the refrigerant flowing through the economizer flow passage 15 is reverse, the refrigerant flows from the economizer port 16 of the economizer flow passage 15 toward the outside of the casing 1. That is, the refrigerant flows from a portion of the first flow passage 15a between the valve 50A and the compression chamber 11, through the valve 50A, and in a direction toward the second flow passage 15b.

[0098] In this case, the valve element 52 is pressed against the valve seat 51b by the flow of refrigerant flowing back from the compression chamber 11. The refrigerant flowing back from the compression chamber 11 presses against the second surface 52d of the valve element 52, pressing the valve element 52 against the valve seat 51b. The spring 55 also presses against the second surface 52d of the valve element 52, pressing the valve element 52 against the valve seat 51b. The valve element 52 seats on the valve seat 51b, closing the end surface opening 51e1 and stopping the flow of refrigerant. In the screw compressor 100, as shown in the area surrounded by the dashed line E, when the valve element 52 seats on the valve seat 51b, the end surface opening 51e1 is closed by the valve element 52, and the economizer flow path 15 is closed.

[0099] Due to the balance between the pressure of the refrigerant and the force of the spring 55, the valve body 52 seats on the valve seat portion 51b to close the end face opening 51e1, or moves away from the valve seat portion 51b to open the end face opening 51e1, thereby connecting the first flow path 15a and the second flow path 15b via the side opening 51f.

[0100] [Operation and Effect of Screw Compressor 100] At least one economizer flow path 15 of the screw compressor 100 according to the second embodiment includes a first flow path 15a and a second flow path 15b. When viewed in a direction perpendicular to the axial direction of the screw shaft 9, the first flow path 15a is formed on a virtual axis that intersects with the screw shaft 9. The first flow path 15a has one end, the economizer port 16, communicating with the compression chamber 11, and the other end, the outer peripheral end 15a1, opposite the compression chamber 11, which is closed. The second flow path 15b is formed to extend along the axial direction of the screw shaft 9. The second flow path 15b has one end, the inner end 15b1, which is the end on the compression chamber 11 side, that intersects with and communicates with the first flow path 15a, and the other end, the outer end 15b2, opposite the compression chamber 11, that is connected to the outside of the casing 1. Since the economizer flow passage 15 is configured as described above, the first flow passage 15a can be formed by machining a through hole from the outside of the casing 1 toward the compression chamber 11. Furthermore, the second flow passage 15b can be formed by machining a through hole from the end face side of the casing 1 toward the first flow passage 15a. Therefore, the economizer flow passage 15 can be easily formed without using complex machining.

[0101] The valve 50A is disposed at the intersection of the first flow path 15a and the second flow path 15b. The valve 50A includes a cylindrical housing 51 having a valve seat 51b formed at one end. The valve 50A is disposed within the housing 51 and is movable along the axial direction of the housing 51. The valve 50A includes a cylindrical valve element 52 that seats on the valve seat 51b to stop the flow of refrigerant when the valve 50A is closed and moves away from the valve seat 51b to allow the refrigerant to pass when the valve 50A is open. The valve 50A also includes a spring 55 disposed within the housing 51 and biases the valve element 52 toward the valve seat 51b. A side opening 51f, which is a through-hole communicating with the first flow path 15a, is formed in the outer peripheral surface of the housing 51. An end opening 51e1, which is a through-hole communicating with the second flow path 15b and whose periphery forms the valve seat 51b, is formed in the end surface of the housing 51. The side opening 51f and the end opening 51e1 form part of the economizer flow path 15. The valve element 52 seats on the valve seat 51b and closes the end opening 51e1 due to the balance between the refrigerant pressure and the biasing force of the spring 55. Alternatively, the valve element 52 moves away from the valve seat 51b and opens the end opening 51e1 due to the balance between the refrigerant pressure and the biasing force of the spring 55, thereby connecting the first flow path 15a and the second flow path 15b via the side opening 51f.

[0102] By providing the valve 50A having the above configuration in the economizer flow path 15, the screw compressor 100 can reduce the amount of refrigerant that flows back from the compression chamber 11 to the economizer pipe 107 outside the casing 1, even when the economizer flow path is closed, thereby reducing dead volume loss. Therefore, the screw compressor 100 can reduce power loss even under low compression ratio conditions with a low economizer flow rate, or when the economizer flow path is closed, and can improve performance particularly during partial load operation.

[0103] Moreover, the screw compressor 100 according to the second embodiment can exert the same effects as the screw compressor 100 according to the first embodiment. Moreover, the refrigeration cycle apparatus 200 according to the second embodiment has the screw compressor 100 according to the second embodiment, and therefore can exert the same effects as the screw compressor 100 according to the second embodiment.

[0104] Third Embodiment. FIG. 16 is a schematic diagram showing a high-pressure side end face portion of the casing 1 in a screw compressor 100 according to a third embodiment. FIG. 17 is a schematic diagram of a cross section taken along the screw shaft 9 of the screw compressor 100 according to the third embodiment. FIG. 18 is a side view of the bearing housing 30 of the screw compressor 100 according to the third embodiment. FIG. 19 is a schematic diagram of a cross section taken along the screw shaft 9 of another example of the screw compressor 100 according to the third embodiment. Note that FIG. 18 is a side view of the bearing housing 30 as seen in the direction of arrow F in FIG. 16. In the third embodiment, the configuration of part of the economizer flow path 15 is specified. The other configurations are the same as or equivalent to those of the first or second embodiment. The following description will focus on the configurations of the third embodiment that are different from the first or second embodiment, and the configurations not described in the third embodiment are the same as those of the first or second embodiment. The configuration of the economizer flow path 15 will be described using FIGS. 16 to 19.

[0105] The screw compressor 100 according to the third embodiment shows an example of the configuration of the flow path between the outer end 15 b 2 of the second flow path 15 b and the outside of the casing 1 with respect to the economizer flow path 15 .

[0106] The screw compressor 100 has a high-pressure side bearing 2 that rotatably supports the end of the screw shaft 9, and a cylindrical bearing housing 30 that houses the bearing 2 and in which part of the economizer flow path 15 is formed. The bearing housing 30 is provided so as to be located at the high-pressure side end face portion of the casing 1.

[0107] The bearing housing 30 has a groove portion 31 constituting a groove formed in an annular shape along the outer periphery of the high-pressure side bearing 2 when the casing 1 is viewed in the axial direction of the screw shaft 9. The groove portion 31 is formed in an annular shape so as to surround the high-pressure side bearing 2 when the casing 1 is viewed in the axial direction of the screw shaft 9. The groove portion 31 is formed so as to be recessed from the end face of the bearing housing 30 on the side where the electric motor 8 is not disposed in the direction where the electric motor 8 is disposed. In other words, the groove portion 31 is recessed in the same direction as the direction from the outer end portion 15b2 side toward the inner end portion 15b1 side of the second flow path 15b.

[0108] The bearing housing 30 has at least one first hole 32 constituting a through-hole that connects the groove 31 and the outer end 15b2 of the second flow path 15b. The first hole 32 is formed to penetrate the wall between the groove 31 and the outer peripheral surface 30a of the bearing housing 30. The first hole 32 opens to the groove 31 and the outer peripheral surface 30a of the bearing housing 30. A connection flange 25a is provided at the end of the casing 1. The connection flange 25a is located on the high-pressure side of the casing 1 and serves as a cover for the end of the casing 1. The connection flange 25a may include a slide valve control mechanism. In this embodiment, the connection flange 25a closes the high-pressure side ends of the second flow path 15b and the flow paths, such as the groove 31, of the bearing housing 30 in the axial direction of the screw shaft 9. The connection flange 25a may also form part of the wall of the first hole 32.

[0109] The bearing housing 30 also has at least one second hole 33 formed at a different position in the circumferential direction of the bearing housing 30 from each of the at least one first hole 32, and constituting a through hole that connects the groove 31 to the outside of the bearing housing 30. The second hole 33 is formed to penetrate the wall between the groove 31 and the outer peripheral surface 30a of the bearing housing 30. The second hole 33 opens to the groove 31 and the outer peripheral surface 30a of the bearing housing 30. The groove 31, the first hole 32, and the second hole 33 formed in the bearing housing 30 constitute a refrigerant flow path 34 of the bearing housing 30 and form part of the economizer flow path 15. That is, the refrigerant flow path 34 through which the refrigerant flows is formed inside the bearing housing 30 as part of the economizer flow path 15, and the refrigerant flow path 34 is connected to the second flow path 15b.

[0110] 16 and 17 , a plurality of economizer flow passages 15 are formed in a casing 1. A plurality of first holes 32 and second holes 33 constituting through holes that connect the grooves 31 to the outside of the bearing housing 30 are formed in a bearing housing 30. In the screw compressor 100, the refrigerant that flows from the second holes 33 into the grooves 31 is supplied to the second flow passages 15 b of the plurality of economizer flow passages 15 via the plurality of first holes 32.

[0111] When the casing 1 is viewed in the axial direction of the screw shaft 9, one third flow path 15c is formed extending therethrough. The third flow path 15c is a through-hole that connects the outside of the casing 1 with at least one of the second holes 33 of the bearing housing 30. The third flow path 15c constitutes at least a portion of the flow path connecting the outside of the casing 1 with the second hole 33. The third flow path 15c is formed to extend between the outer circumferential surface 1b of the casing 1 and the bearing housing 30. The third flow path 15c extends, for example, on a virtual axis that intersects with the cylindrical bearing housing 30. In FIG. 16 , the axis CA1 indicates the virtual axis that intersects with the bearing housing 30. Note that the third flow path 15c does not necessarily have to extend on the axis CA1. For example, as shown in FIG. 19 , the casing 1 may have a space S formed between the third flow path 15c and the second hole 33. In the screw compressor 100, when the casing 1 is viewed in the axial direction of the screw shaft 9, the open end 17a, the third flow path 15c, and the second hole portion 33 may not be aligned in a straight line.

[0112] The third flow path 15c constitutes a part of the economizer flow path 15. The third flow path 15c is in communication with the second flow path 15b of the casing 1 via a groove 31, a first hole 32, and a second hole 33 formed in the bearing housing 30.

[0113] The economizer flow path 15 of the screw compressor 100 includes a first flow path 15a, a second flow path 15b, a groove 31, a plurality of first holes 32, a second hole 33, and a third flow path 15c. More specifically, the economizer flow path 15 of the screw compressor 100 includes the first flow path 15a, the second flow path 15b, and the third flow path 15c formed in the casing 1, and further includes the groove 31, the first hole 32, and the second hole 33 formed in the bearing housing 30.

[0114] [Operation and Effect of Screw Compressor 100] The screw compressor 100 has a bearing 2 that rotatably supports an end of the screw shaft 9, and a cylindrical bearing housing 30 that houses the bearing 2 and in which part of the economizer flow path 15 is formed. A refrigerant flow path 34 through which a refrigerant flows is formed inside the bearing housing 30 as part of the economizer flow path 15, and the refrigerant flow path 34 is connected to the second flow path 15b.

[0115] In the screw compressor 100 according to the third embodiment, the refrigerant flow path 34 of the bearing housing 30 constitutes part of the economizer flow path 15, and therefore, even when the screw compressor 100 has the first flow path 15a and the second flow path 15b as in the second embodiment, it is easy to form the opening end 17a on the outer peripheral surface 1b side of the casing 1.

[0116] By providing the valve 50A in the economizer flow path 15 configured as described above, the screw compressor 100 can reduce the amount of refrigerant that flows back from the compression chamber 11 to the economizer pipe 107 outside the casing 1, even when the economizer flow path is closed, thereby reducing dead volume loss. Therefore, the screw compressor 100 can reduce power loss even under low compression ratio conditions with a low economizer flow rate, or when the economizer flow path is closed, and can improve performance particularly during partial load operation.

[0117] Furthermore, the bearing housing 30 has a groove portion 31 that forms a groove formed in an annular shape along the outer periphery of the bearing 2 when the casing 1 is viewed in the axial direction of the screw shaft 9. Furthermore, the bearing housing 30 has at least one first hole portion 32 that forms a through hole that connects the groove portion 31 and the outer end portion 15b2 of the second flow path 15b.

[0118] The screw compressor 100 according to embodiment 3 utilizes the groove portion 31 and the first hole portion 32 of the bearing housing 30, making it easy to form the opening end 17a on the outer peripheral surface 1b side of the casing 1 even when the screw compressor 100 has the first flow path 15a and the second flow path 15b.

[0119] A plurality of economizer flow passages 15 are formed in the casing 1. A plurality of first holes 32 and second holes 33 constituting through holes that connect the grooves 31 to the outside of the bearing housing 30 are formed in the bearing housing 30. In the screw compressor 100, the refrigerant that flows into the grooves 31 from the second holes 33 is supplied to the second flow passages 15b of the plurality of economizer flow passages 15 via the plurality of first holes 32.

[0120] As shown in Fig. 16, the screw compressor 100 has a bearing housing 30 having a groove 31, a first hole 32, and a second hole 33, which allows one third flow path 15c to communicate with two or more second flow paths 15b. That is, when the screw compressor 100 has two or more second flow paths 15b, the second flow paths 15b can be communicated with the outside of the casing 1 through one second hole 33. Therefore, the screw compressor 100 only needs to form one third flow path 15c that communicates with the second hole 33, which ensures the strength of the casing 1 compared to when multiple third flow paths 15c are provided. Furthermore, the screw compressor 100 requires fewer processing steps and is easier to manufacture compared to when multiple third flow paths 15c are provided.

[0121] The casing 1 also has a third flow path 15c formed therein, which is a through hole that connects the outside of the casing 1 with the second hole portion 33 and constitutes at least a part of a flow path connecting the outside of the casing 1 with the second hole portion 33. The economizer flow path 15 of the screw compressor 100 includes a first flow path 15a, a second flow path 15b, a groove portion 31, each of the plurality of first hole portions 32, the second hole portion 33, and the third flow path 15c.

[0122] By providing the valve 50A in the economizer flow path 15 configured as described above, the screw compressor 100 can reduce the amount of refrigerant that flows back from the compression chamber 11 to the economizer pipe 107 outside the casing 1, even when the economizer flow path is closed, thereby reducing dead volume loss. Therefore, the screw compressor 100 can reduce power loss even under low compression ratio conditions with a low economizer flow rate, or when the economizer flow path is closed, and can improve performance particularly during partial load operation.

[0123] 16 , the screw compressor 100 has a bearing housing 30 having a groove 31, a first hole 32, and a second hole 33, which allows one third flow path 15c to communicate with two or more second flow paths 15b. That is, when the screw compressor 100 has two or more second flow paths 15b, the second flow paths 15b can be connected to the outside of the casing 1 via one third flow path 15c. Therefore, the screw compressor 100 can ensure the strength of the casing 1 compared to when multiple third flow paths 15c are provided. Furthermore, the screw compressor 100 requires fewer processing steps and is easier to manufacture compared to when multiple third flow paths 15c are provided.

[0124] Furthermore, since the economizer flow path 15 is configured as described above, the first flow path 15a can be formed by machining a through hole from the outside of the casing 1 toward the compression chamber 11. The second flow path 15b can be formed by machining a through hole from the end face side of the casing 1 toward the first flow path 15a. Therefore, the economizer flow path 15 can be easily formed without using complex machining.

[0125] Moreover, the screw compressor 100 according to the third embodiment can exert the same effects as the screw compressor 100 according to the first or second embodiment. Moreover, the refrigeration cycle apparatus 200 according to the third embodiment has the screw compressor 100 according to the third embodiment, and therefore can exert the same effects as the screw compressor 100 according to the third embodiment.

[0126] The configurations described in the above embodiments are merely examples of the contents of the present disclosure, and may be combined with other known technologies. Parts of the configuration may be omitted or modified without departing from the spirit and scope of the present disclosure. For example, the valves 50 and 50A are not limited to the structures described in the first and second embodiments. They may be any valves with a check function, such as thin, rectangular reed valves. Furthermore, the first to third embodiments may be combined. For example, the valve 50 according to the first embodiment may be applied to the economizer flow path 15 according to the second embodiment.

[0127] DESCRIPTION OF SYMBOLS 1 Casing, 1A Storage section, 1a Gate rotor opening, 1b Outer circumferential surface, 1e Opposing surface, 1f End surface, 2 Bearing, 3 Bearing, 4 Screw rotor, 5 Gate rotor support, 5a Bearing, 5b Central shaft, 6 Gate rotor support chamber, 7 Gate rotor, 7a Tooth portion, 8 Motor, 8a Stator, 8b Rotor, 9 Screw shaft, 10 Screw groove, 11 Compression chamber, 12 Slide valve, 14 Slide groove, 15 Economizer flow path, 15a First flow path, 15a1 Outer circumferential end, 15a2 Blocking member, 15b Second flow path, 15b1 Inner end, 15b2 Outer end, 15c Third flow path, 16 Economizer port, 17 Open end, 17a Open end, 18 Discharge port, 19 Step portion, 20 Compression section, 25 Connection flange, 25a REFRIGERATED SYMBOLS, 30, BEARING HOUSING, 30a, OUTER PERIPHERAL SURFACE, 31, GROOVE, 32, FIRST HOLE, 33, SECOND HOLE, 34, REFRIGERATED FLOW PATH, 50, VALVE, 50A, VALVE, 51, HOUSING, 51A, HOUSING, 51a, CYLINDER, 51a1, CYLINDER, 51b, VALVE SEAT, 51c, SUPPORT, 51c1, CENTRAL, 51c2, OUTER PERIPHERAL, 51c3, BRIDGING, 51d1, FIRST THRU-HOLE, 51d2, SECOND THRU-HOLE, 51e, CENTRAL THRU-HOLE, 51e1, END SURFACE OPENING, 51f, SIDING OPENING, 52, VALVE BODY, 52a, VALVE BODY UPPER PART, 52b, VALVE BODY LOWER PART, 52c, FIRST SURFACE, 52d, SECOND SURFACE, 54, RETAINING RIVER, 55, SPRING, 100, SCREW COMPRESSOR, 101, INVERTER, 102, CONDENSER, 103, INTERCOILER, 103a High pressure section, 103b low pressure section, 104 expansion valve, 105 evaporator, 106 intercooler expansion valve, 107 economizer piping, 200 refrigeration cycle device, 201 refrigerant piping, 202 refrigerant circuit, 203 branch circuit, 210 control device.

Claims

1. A screw compressor used in an economizer cycle in which a refrigerant is injected into a compression chamber during a compression process, comprising: a compression section having a screw shaft that serves as a rotating shaft and compressing the refrigerant; a casing that houses the compression section and constitutes the compression chamber together with the compression section; and a valve that allows the refrigerant to pass in one direction, wherein at least one economizer flow path is formed inside the casing, the flow path being used for injecting the refrigerant and connecting the outside of the casing with the compression chamber, and wherein the valve that prevents backflow of the refrigerant is disposed in each of the at least one economizer flow path.

2. A screw compressor as described in claim 1, wherein each of the at least one economizer flow passages is formed in the casing and extends so as to communicate between the outside of the casing and the compression chamber when the casing is viewed in the axial direction of the screw shaft, and is formed in the casing and extends on a virtual axis line intersecting the screw shaft when viewed in a direction perpendicular to the axial direction of the screw shaft.

3. The screw compressor according to claim 1 or 2, wherein each of the at least one economizer flow passages includes: a first flow passage which is formed on an imaginary axis intersecting the screw shaft when viewed in a direction perpendicular to the axial direction of the screw shaft, and has an economizer port at one end which communicates with the compression chamber and an outer circumferential end at the other end opposite the compression chamber which is closed; and a second flow passage which is formed to extend along the axial direction of the screw shaft, and has an inner end side which is one end on the compression chamber side and intersects with and communicates with the first flow passage, and an outer end side which is the other end opposite the compression chamber and communicates with the outside of the casing.

4. A screw compressor as claimed in any one of claims 1 to 3, wherein the valve is a check valve which allows the refrigerant flowing into the compression chamber from outside the casing to pass and prevents the refrigerant from flowing out of the compression chamber to outside the casing.

5. The screw compressor according to any one of claims 1 to 4, wherein each of the at least one economizer flow passages is formed with a stepped portion where an opening diameter becomes smaller in a direction from the outside of the casing toward the compression chamber, and the valve comprises: a housing formed in a cylindrical shape, a support portion forming one end thereof is disposed in the stepped portion and a valve seat portion forming the other end thereof is fixed to each of the at least one economizer flow passages by a retaining ring; and a valve disc disposed movably inside the housing and moved by the pressure of the refrigerant, wherein the valve disc is formed in a cylindrical shape, a valve disc lower portion inserted into the support portion and supported by the support portion so as to be movably supported by the support portion, and an valve disc upper portion formed in a cylindrical shape with a diameter larger than that of the valve disc lower portion, and seated on the valve seat portion to stop the flow of the refrigerant when the valve is closed, and seated on the support portion to allow the refrigerant to pass when the valve is opened.

6. The valve is disposed at an intersection between the first flow path and the second flow path, the valve comprising: a housing formed in a cylindrical shape and having a valve seat portion formed at one end; a cylindrical valve body disposed within the housing and movable along the axial direction of the housing, and seated on the valve seat portion to stop the flow of the refrigerant when the valve is closed and separated from the valve seat portion to allow the refrigerant to pass when the valve is opened; and a spring disposed within the housing and biasing the valve body toward the valve seat portion, wherein a side opening portion which is a through hole communicating with the first flow path is formed on an outer circumferential surface of the housing, and an end opening portion which is a through hole communicating with the second flow path and has a periphery which constitutes the valve seat portion is formed on an end surface of the housing, the side opening portion and the end opening portion constitute a part of the economizer flow path, and the valve body is 4. The screw compressor according to claim 3, wherein, depending on a balance between a pressure of the refrigerant and a biasing force of the spring, the valve seat is seated on the valve seat portion to close the end face opening, or is separated from the valve seat portion to open the end face opening, thereby communicating the first flow path and the second flow path via the side opening.

7. A screw compressor as claimed in claim 3 or 6, comprising: a bearing for rotatably supporting an end of the screw shaft; and a cylindrical bearing housing for accommodating the bearing and in which a part of the economizer flow path is formed, wherein a refrigerant flow path through which the refrigerant flows is formed inside the bearing housing as part of the economizer flow path, and the refrigerant flow path and the second flow path are connected.

8. A screw compressor as described in claim 7, wherein the bearing housing has, when the casing is viewed in the axial direction of the screw shaft, a groove portion constituting a groove formed in an annular shape along the outer periphery of the bearing, and at least one first hole portion constituting a through hole connecting the groove portion and the outer end portion of the second flow path.

9. A screw compressor as described in claim 8, wherein a plurality of the economizer flow paths are formed in the casing, and a plurality of the first hole portions and a second hole portion constituting a through hole connecting the groove portion with the outside of the bearing housing are formed in the bearing housing, and the refrigerant flowing into the groove portion from the second hole portion is supplied to the second flow path of each of the plurality of the economizer flow paths via the plurality of the first hole portions.

10. A screw compressor as described in claim 9, wherein the casing is formed with a third flow passage constituting at least a part of a flow passage connecting the outside of the casing and the second hole portion, and the economizer flow passage includes the first flow passage, the second flow passage, the groove portion, a plurality of the first hole portions, the second hole portions, and the third flow passage.

11. A refrigeration cycle apparatus comprising: the screw compressor according to any one of claims 1 to 10; a condenser that condenses the refrigerant; an expansion valve that reduces the pressure of the refrigerant flowing inside; an intercooler having a high-pressure section through which the refrigerant flowing out of the condenser flows and a low-pressure section into which the refrigerant flowing out of the high-pressure section flows, and disposed between the condenser and the expansion valve; an evaporator that evaporates the refrigerant; an intercooler expansion valve that reduces the pressure of the refrigerant flowing out of the high-pressure section of the intercooler and flows it into the low-pressure section of the intercooler; refrigerant piping that constitutes a refrigerant circuit that sequentially connects the screw compressor, the condenser, the high-pressure section of the intercooler, the expansion valve, and the evaporator; and economizer piping that branches off between the intercooler and the expansion valve, and constitutes a branch circuit that is connected to the economizer flow path of the screw compressor via the intercooler expansion valve and the low-pressure section of the intercooler.

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