Refrigeration device

Abstract

The refrigeration device using an R454C refrigerant has, as compared with the refrigeration device using an R32 refrigerant, a higher ratio of a discharge pressure to a suction pressure of a compressor, and a larger impact load applied to a bearing portion of a crankshaft, so that the bearing portion is easily damaged. An air conditioning device (1) comprises a refrigerant circuit (10) and an outdoor unit control unit (71). The refrigerant circuit (10) has a compressor (11). The refrigerant circuit (10) circulates a refrigerant by the compressor (11) to perform a refrigeration cycle. The outdoor unit control unit (71) performs control relating to the refrigeration cycle. The compressor (11) has a compression chamber (Sc) in which the refrigerant is compressed, and an injection pipe (53) that communicates with the compression chamber (Sc). A ratio of a discharge pressure to a suction pressure of the compressor (11) is 4.5 times or more and 6.25 times or less a compression ratio of the compression chamber (Sc). The outdoor unit control unit (71) performs control such that a first ratio, which is a ratio of the flow rate of the refrigerant flowing through the injection pipe (53) to the flow rate of the refrigerant circulating through the refrigerant circuit (10), is 79% or more.

Description

Refrigeration device

[0001] It relates to a refrigeration device.

[0002] Patent Document 1 (Japanese Patent Application Laid-Open No. 2018-184872) discloses a refrigeration device including a scroll compressor that compresses R32 refrigerant. In recent years, the adoption of R454C refrigerant with a lower global warming potential (GWP) than R32 refrigerant has been progressing.

[0003] During the operation of the scroll compressor, when the discharge port of the compression mechanism opens, the high-pressure refrigerant in the refrigerant circuit flows backward into the compression mechanism, and an impact load is applied to the bearing portion of the crankshaft. A refrigeration device using R454C refrigerant has a higher ratio of the discharge pressure to the suction pressure of the compressor and a larger impact load compared to a refrigeration device using R32 refrigerant, so the bearing portion is likely to be damaged.

[0004] The refrigeration device of the first aspect includes a refrigerant circuit and a control unit. The refrigerant circuit has a compressor. The refrigerant circuit circulates the refrigerant by the compressor to perform a refrigeration cycle. The control unit performs control related to the refrigeration cycle. The compressor has a compression chamber where the refrigerant is compressed and an injection passage communicating with the compression chamber. The ratio of the discharge pressure to the suction pressure of the compressor is 4.5 times or more and 6.25 times or less of the compression ratio of the compression chamber. The control unit performs control such that a first ratio, which is the ratio of the flow rate of the refrigerant flowing through the injection passage to the flow rate of the refrigerant circulating through the refrigerant circuit, is 79% or more.

[0005] The refrigeration device of the first aspect suppresses damage to the bearing portion by suppressing the impact load applied to the bearing portion of the crankshaft by increasing the flow rate of the refrigerant injected into the compression chamber when the operating pressure ratio of the compressor is high.

[0006] The refrigeration device of the second aspect is the refrigeration device of the first aspect, and the control unit further performs control such that the pressure of the refrigerant flowing through the injection passage is lower than the discharge pressure.

[0007] The refrigeration device of the second aspect reduces bearing stress and suppresses damage to the bearing portion.

[0008] The third refrigeration device is the first or second refrigeration device, and the control unit further performs control such that the first ratio is 381% or less.

[0009] The third aspect of the refrigeration system suppresses damage to the bearing by ensuring that the impact load applied to the bearing by refrigerant injection does not exceed a predetermined upper limit.

[0010] The refrigeration system of the fourth aspect is a refrigeration system of any one of the first to third aspects, wherein the ratio of discharge pressure to suction pressure is 18 or more and 25 or less. The compression ratio is 4 or less.

[0011] The refrigeration system described in the fourth aspect suppresses damage to the bearing section even when the ratio of the compressor's operating pressure ratio to the compressor's design volume ratio is high.

[0012] The fifth aspect of the refrigeration apparatus is a refrigeration apparatus according to any one of the first to fourth aspects, wherein the compressor has a fixed scroll and a movable scroll. The movable scroll, together with the fixed scroll, forms a compression chamber. An injection passage is formed in the fixed scroll.

[0013] The fifth aspect of the refrigeration system suppresses damage to the bearing section even when the ratio of the compressor's operating pressure ratio to the compressor's design volume ratio is high.

[0014] The refrigeration system of the sixth aspect is a refrigeration system of any one of the first to fifth aspects, wherein the refrigerant is R454C or R290.

[0015] The sixth aspect of the refrigeration system suppresses damage to the bearings even when using refrigerants that require operation under conditions of high compressor operating pressure ratio.

[0016] The refrigeration device of the seventh aspect is a refrigeration device according to any one of the first to sixth aspects, wherein the control unit controls the first ratio by adjusting at least one of the flow rate of refrigerant in the high-pressure region of the refrigerant circuit and the flow rate of refrigerant in the low-pressure region of the refrigerant circuit.

[0017] The seventh aspect of the refrigeration system suppresses damage to the bearing section by adjusting the flow rate of the refrigerant injected into the compression chamber.

[0018] The refrigeration system of the eighth aspect is a refrigeration system of any one of the first to seventh aspects, wherein the refrigerant circuit further comprises an expansion valve and piping. The expansion valve reduces the pressure of the high-pressure refrigerant in the refrigeration cycle until it becomes an intermediate-pressure refrigerant. The piping is into which the intermediate-pressure refrigerant flows and is connected to an injection passage. The control unit adjusts the first ratio by controlling the opening of the expansion valve.

[0019] This is a schematic diagram of the air conditioning system 1. This is a schematic cross-sectional view of the compressor 11. This is a diagram showing the high-pressure and low-pressure regions of the refrigerant circuit 10. This is a graph showing the relationship between the first ratio and the impact load. This is a graph showing the relationship between the crank angle and the internal pressure of the vortex.

[0020] (1) Overall Configuration The air conditioning system 1 is a refrigeration system that harmonizes the air in a target space by performing a vapor compression type refrigeration cycle. As shown in Figure 1, the air conditioning system 1 mainly consists of an outdoor unit 2, an indoor unit 3, a gas refrigerant connecting pipe 5, a liquid refrigerant connecting pipe 6, a controller 7, and a remote control 8. The gas refrigerant connecting pipe 5 and the liquid refrigerant connecting pipe 6 connect the outdoor unit 2 and the indoor unit 3.

[0021] In the air conditioning system 1, the refrigerant sealed in the refrigerant circuit 10 is repeatedly compressed, condensed (heat released), depressurized, evaporated (heat absorbed), and then compressed again in a refrigeration cycle.

[0022] The refrigerant circuit 10 is sealed with refrigerant and refrigerant oil. The refrigerant oil is mainly used to lubricate the sliding parts of the mechanism for compressing the refrigerant. It is preferable that the compatibility between the refrigerant oil and the refrigerant be relatively high so that the refrigerant oil can circulate in the refrigerant circuit 10 together with the refrigerant. On the other hand, if the compatibility between the refrigerant oil and the refrigerant is too high, the viscosity of the refrigerant oil may decrease as the refrigerant dissolves into it, which may reduce the lubricity of the refrigerant oil. Therefore, it is preferable to select an appropriate refrigerant oil according to the refrigerant so that the compatibility between the refrigerant oil and the refrigerant is within an appropriate range.

[0023] Refrigerant oil, for example, contains polyalkylene glycol (PAG) as its main component. PAG is, for example, polyethylene glycol, polypropylene glycol, and copolymer compounds of polyethylene glycol and polypropylene glycol. The refrigerant oil may be a refrigerant consisting solely of PAG, or it may be a mixture of PAG and a lubricating oil other than PAG. The lubricating oil other than PAG is, for example, mineral oil and alkylbenzene. The refrigerant oil preferably contains at least one additive selected from the group consisting of extreme pressure agents, acid scavengers, and antioxidants. These additives are preferably blended into the refrigerant oil at a concentration of 5.0 wt% or less.

[0024] (1-1) Outdoor Unit 2 The outdoor unit 2 is connected to the indoor unit 3 via gas refrigerant connecting pipe 5 and liquid refrigerant connecting pipe 6, and constitutes part of the refrigerant circuit 10. The outdoor unit 2 mainly includes a compressor 11, a four-way switching valve 12, an outdoor heat exchanger 13, a first expansion valve 9, a low-pressure receiver 14, an outdoor fan 15, a gas-side shut-off valve 16, a liquid-side shut-off valve 17, an intermediate heat exchanger 27, and a second expansion valve 28.

[0025] The compressor 11 is a device that compresses the low-pressure refrigerant in the refrigeration cycle until it reaches high pressure. The compressor 11 compresses the refrigerant in the compression chamber by changing the volume of the compression chamber through rotational drive of the compression element by the compressor motor. The operating frequency of the compressor motor can be controlled by an inverter.

[0026] The four-way switching valve 12 switches between a first connection state (solid line in Figure 1) and a second connection state (dotted line in Figure 1) by switching the connection state of the refrigerant circuit 10. In the first connection state, the discharge side of the compressor 11 is connected to the outdoor heat exchanger 13, and the suction side of the compressor 11 is connected to the gas side shut-off valve 16. In the second connection state, the discharge side of the compressor 11 is connected to the gas side shut-off valve 16, and the suction side of the compressor 11 is connected to the outdoor heat exchanger 13. The four-way switching valve 12 has four connection ports.

[0027] The outdoor heat exchanger 13 functions as a condenser or heat exchanger for high-pressure refrigerant in the refrigeration cycle during cooling operation, and as an evaporator or heat absorber for low-pressure refrigerant in the refrigeration cycle during heating operation. The outdoor heat exchanger 13 has a plurality of heat transfer tubes (not shown) through which refrigerant flows, and a plurality of heat transfer fins (not shown) through which air flows. The plurality of heat transfer tubes are arranged vertically, and each heat transfer tube extends substantially horizontally. The material of the heat transfer tubes is, for example, copper, copper alloy (brass, etc.), and stainless steel (SUS304, etc.). The plurality of heat transfer fins extending vertically are arranged at predetermined intervals from each other along the direction in which the heat transfer tubes extend. The plurality of heat transfer fins and the plurality of heat transfer tubes are combined such that each heat transfer fin is passed through a plurality of heat transfer tubes.

[0028] The outdoor fan 15 supplies outdoor air to the outdoor heat exchanger 13, and after heat exchange with the refrigerant in the outdoor heat exchanger 13, it generates an airflow for discharge to the outside of the outdoor unit 2. The outdoor fan 15 is rotationally driven by an outdoor fan motor.

[0029] The first expansion valve 9 is located between the liquid-side end of the outdoor heat exchanger 13 and the liquid-side shut-off valve 17. The first expansion valve 9 is an electronically controlled expansion valve whose valve opening can be adjusted by electronic control.

[0030] The low-pressure receiver 14 is located between the suction side of the compressor 11 and one of the four connection ports of the four-way switching valve 12. The low-pressure receiver 14 is a refrigerant container capable of storing excess refrigerant in the refrigerant circuit 10 as liquid refrigerant.

[0031] The gas-side shut-off valve 16 is a manual valve located inside the outdoor unit 2 at the connection point with the gas refrigerant communication pipe 5.

[0032] The liquid side shut-off valve 17 is a manual valve located inside the outdoor unit 2 at the connection point with the liquid refrigerant communication pipe 6.

[0033] The intermediate heat exchanger 27 has a first heat exchange section 27a and a second heat exchange section 27b. The intermediate heat exchanger 27 performs heat exchange between a first refrigerant flowing through the first heat exchange section 27a and a second refrigerant flowing through the second heat exchange section 27b. The flow direction of the first refrigerant is opposite to the flow direction of the second refrigerant.

[0034] One end of the first heat exchange section 27a is connected to the liquid side end of the outdoor heat exchanger 13 by the first pipe 61. The other end of the first heat exchange section 27a is connected to the first expansion valve 9 by the second pipe 62. One end of the second heat exchange section 27b is connected to the second expansion valve 28 by the third pipe 63. The other end of the second heat exchange section 27b is connected to the compressor 11 by the fourth pipe 64.

[0035] The second expansion valve 28 is connected to the third piping 63 and the fifth piping 65 which branches off from the first piping 61. The second expansion valve 28 is an electronically controlled expansion valve whose valve opening can be adjusted by electronic control. The second expansion valve 28 reduces the pressure of the high-pressure refrigerant in the refrigeration cycle until it reaches an intermediate pressure. An intermediate pressure refrigerant is a refrigerant with a pressure higher than the low-pressure refrigerant in the refrigeration cycle and lower than the high-pressure refrigerant in the refrigeration cycle.

[0036] The intermediate heat exchanger 27 performs heat exchange between the first refrigerant, which has been heated by the outdoor heat exchanger 13 and before being depressurized by the first expansion valve 9, and the second refrigerant, which has been heated by the outdoor heat exchanger 13 and after being depressurized by the second expansion valve 28.

[0037] After heat exchange in the outdoor heat exchanger 13, a portion of the high-pressure refrigerant flowing through the first pipe 61 flows into the fifth pipe 65 and is depressurized by the second expansion valve 28 to become intermediate-pressure refrigerant. The intermediate-pressure refrigerant passes through the third pipe 63 and then flows into the second heat exchange section 27b. In the intermediate heat exchanger 27, heat exchange takes place between the high-pressure refrigerant that flows through the first pipe 61 and then through the first heat exchange section 27a, and the intermediate-pressure refrigerant that passes through the second heat exchange section 27b. The high-pressure refrigerant that has been heat-exchanged in the first heat exchange section 27a flows into the second pipe 62 and is depressurized by the first expansion valve 9 to become low-pressure refrigerant. The intermediate-pressure refrigerant that has been heat-exchanged in the second heat exchange section 27b flows into the fourth pipe 64 and is supplied to the compressor 11.

[0038] The outdoor unit 2 has an outdoor unit control unit 71 that controls the operation of each part that makes up the outdoor unit 2. The outdoor unit control unit 71 has a microcomputer including a CPU and memory. The outdoor unit control unit 71 is connected to the indoor unit control unit 72 of each indoor unit 3 via a communication line and transmits and receives control signals and the like.

[0039] (1-2) Indoor Unit 3 The indoor unit 3 is installed on the walls and ceiling of the room that is the target space. The indoor unit 3 is connected to the outdoor unit 2 via gas refrigerant connecting pipe 5 and liquid refrigerant connecting pipe 6, and constitutes part of the refrigerant circuit 10. The indoor unit 3 mainly consists of an indoor heat exchanger 18 and an indoor fan 19.

[0040] The liquid-side end of the indoor heat exchanger 18 is connected to the liquid refrigerant connecting pipe 6. The gas-side end of the indoor heat exchanger 18 is connected to the gas refrigerant connecting pipe 5. During cooling operation, the indoor heat exchanger 18 functions as an evaporator or heat absorber for the low-pressure refrigerant in the refrigeration cycle, and during heating operation, it functions as a condenser or heat radiator for the high-pressure refrigerant in the refrigeration cycle. Similar to the outdoor heat exchanger 13, the indoor heat exchanger 18 has a plurality of heat transfer tubes (not shown) through which the refrigerant flows, and a plurality of heat transfer fins (not shown) through which air flows.

[0041] The indoor fan 19 draws in indoor air, which is the target space, and generates an airflow to discharge it to the outside of the indoor unit 3 after it has exchanged heat with the refrigerant in the indoor heat exchanger 18. The indoor fan 19 is rotationally driven by an indoor fan motor.

[0042] The indoor unit 3 has an indoor unit control unit 72 that controls the operation of each part that constitutes the indoor unit 3. The indoor unit control unit 72 has a microcomputer including a CPU and memory. The indoor unit control unit 72 is connected to the outdoor unit control unit 71 via a communication line and transmits and receives control signals and the like.

[0043] (1-3) Controller 7 In the air conditioner 1, an outdoor unit control unit 71 and an indoor unit control unit 72 are connected via a communication line, thereby constituting a controller 7 that controls the operation of the air conditioner 1. The controller 7 mainly includes a CPU and memories such as a ROM and a RAM. Various processes and controls by the controller 7 are realized by the integrated functions of each part included in the outdoor unit control unit 71 and the indoor unit control unit 72.

[0044] The controller 7 controls the components of the refrigerant circuit 10 via the outdoor unit control unit 71 and the indoor unit control unit 72. The control targets by the controller 7 are, for example, the first expansion valve 9, the second expansion valve 28, the compressor 11, the four-way switching valve 12, the outdoor fan 15, the indoor fan 19, and the remote controller 8. The controller 7 controls the components of the refrigerant circuit 10 so that the temperature of the fluid (refrigerant and refrigerant oil) flowing in the refrigerant circuit 10 of the air conditioner 1 becomes a predetermined temperature or lower. Examples of such control include control to prevent the driving frequency of the compressor 11 from exceeding a predetermined value, control to prevent the temperature of the refrigerant discharged from the compressor 11 from exceeding a predetermined temperature, and control to prevent the pressure of the refrigerant discharged from the compressor 11 from exceeding a predetermined pressure.

[0045] (1-4) Remote controller 8 The remote controller 8 is installed in the indoor space which is the target space or a specific space of a building including the target space, and is used by a user or the like to issue an operation control command for the air conditioner 1 and monitor the operation state.

[0046] The remote controller 8 includes a reception part 8a such as an operation button and a touch panel, and a display 8b capable of displaying various information. The reception part 8a receives input of various information when operated by a user or the like. The remote controller 8 is connected to the outdoor unit control unit 71 and the indoor unit control unit 72 via a communication line, and supplies the information received at the reception part 8a from a user or the like to the controller 7. The remote controller 8 outputs the information received from the controller 7 to the display 8b.

[0047] The information received by the reception unit 8a from the user or the like is not particularly limited, and examples thereof include information regarding a command to execute a cooling operation mode, a command to execute a heating operation mode, a command to stop the operation, and a designation to set the temperature. The information displayed on the display 8b is not particularly limited, and examples thereof include the current operation mode (cooling or heating operation mode), the set temperature, and information indicating that various abnormalities have occurred.

[0048] (2) Detailed configuration of the compressor 11 The compressor 11 is a scroll compressor. The compressor 11 sucks in a refrigerant at a low pressure (hereinafter, may be simply referred to as low pressure) in the refrigeration cycle, compresses the sucked refrigerant, and discharges it at a high pressure (hereinafter, may be simply referred to as high pressure) in the refrigeration cycle.

[0049] As shown in FIG. 2, the compressor 11 mainly includes a casing 50, a compression mechanism 20, a housing 60, a motor 70, a crankshaft 80, and a lower housing 130.

[0050] (2-1) Casing 50 The compressor 11 has a vertically long cylindrical casing 50 (see FIG. 2).

[0051] The casing 50 mainly includes a cylindrical member 50a, an upper lid 50b, and a lower lid 50c. The cylindrical member 50a is a cylindrical member that extends along the central axis B and is open at the top and bottom. The upper lid 50b is provided above the cylindrical member 50a and closes the upper opening of the cylindrical member 50a. The lower lid 50c is provided below the cylindrical member 50a and closes the lower opening of the cylindrical member 50a. The cylindrical member 50a, the upper lid 50b, and the lower lid 50c are fixed by welding so as to maintain airtightness.

[0052] The casing 50 houses various components that make up the compressor 11, including the compression mechanism 20, housing 60, motor 70, crankshaft 80, and lower housing 130 (see Figure 2). The compression mechanism 20 is located in the upper part of the casing 50. Below the compression mechanism 20 is the housing 60. Below the housing 60 is the motor 70. Below the motor 70 is the lower housing 130. An oil reservoir space 50d is formed at the bottom of the casing 50. The oil reservoir space 50d contains refrigerant oil for lubricating the various sliding parts of the compressor 11.

[0053] The motor 70 is located in the first space S1 of the compressor 11. The first space S1 is the space inside the casing 50, below the housing 60. In this embodiment, the first space S1 is the space into which high-pressure refrigerant compressed by the compression mechanism 20 flows. In other words, the compressor 11 in this embodiment is a so-called high-pressure dome-type scroll compressor. However, the compressor 11 does not have to be a high-pressure dome-type scroll compressor. The compressor 11 may be a so-called low-pressure dome-type scroll compressor in which the motor is located in the space into which low-pressure refrigerant flows from the refrigerant circuit 10 of the air conditioning system 1.

[0054] The casing 50 is fitted with an intake pipe 51, a discharge pipe 52, and an injection pipe 53 so as to connect the inside and outside of the casing 50 (see Figure 2).

[0055] As shown in Figure 2, the suction pipe 51 is provided passing through the top cover 50b of the casing 50. One end of the suction pipe 51 (the end outside the casing 50) is connected to piping extending from the evaporator of the refrigerant circuit 10 of the air conditioner 1, and the other end of the suction pipe 51 (the end inside the casing 50) is connected to the suction port 36a of the fixed scroll 30 of the compression mechanism 20. The suction pipe 51 communicates with the compression chamber Sc on the outer circumference of the compression mechanism 20, which will be described later, via the suction port 36a. The compressor 11 draws in low-pressure refrigerant from the refrigeration cycle of the air conditioner 1 via the suction pipe 51.

[0056] As shown in Figure 2, the discharge pipe 52 is provided in the central part of the cylindrical member 50a in the vertical direction, penetrating the cylindrical member 50a. One end of the discharge pipe 52 (the end outside the casing 50) is connected to piping extending to the condenser of the refrigerant circuit 10 of the air conditioner 1, and the other end of the discharge pipe 52 (the end inside the casing 50) is positioned between the housing 60 and the motor 70 in the first space S1. The compressor 11 discharges the high-pressure refrigerant, which has been compressed by the compression mechanism 20, through the discharge pipe 52.

[0057] As shown in Figure 2, the injection pipe 53 is installed by penetrating the top cover 50b of the casing 50. One end of the injection pipe 53 (the end outside the casing 50) is connected to the fourth pipe 64 of the refrigerant circuit 10 of the air conditioner 1, and the other end of the injection pipe 53 (the end inside the casing 50) is connected to the fixed scroll 30 of the compression mechanism 20. The injection pipe 53 communicates with the compression chamber Sc of the compression mechanism 20 during the compression process via a passage (not shown) formed in the fixed scroll 30. Refrigerant at an intermediate pressure in the refrigeration cycle is supplied to the compression chamber Sc, which the injection pipe 53 communicates with, from the refrigerant circuit 10 of the air conditioner 1 via the injection pipe 53. Note that the intermediate pressure in the refrigeration cycle refers to the pressure between the low pressure and high pressure in the refrigeration cycle. Hereafter, instead of referring to it as the intermediate pressure in the refrigeration cycle, it may simply be called the intermediate pressure.

[0058] (2-2) Compression mechanism 20 The compression mechanism 20 mainly comprises a fixed scroll 30 and a movable scroll 40. The fixed scroll 30 and the movable scroll 40 are combined to form a compression chamber Sc. The compression mechanism 20 compresses the refrigerant in the compression chamber Sc and discharges the compressed refrigerant.

[0059] (2-2-1) Fixed scroll 30 The fixed scroll 30 is mounted on the housing 60 and fixed to the housing 60 by fixing means (e.g., bolts) not shown.

[0060] As shown in Figure 2, the fixed scroll 30 mainly consists of a fixed end plate 32, a fixed lap 34, and a peripheral edge 36.

[0061] The fixed end plate 32 is a disc-shaped member. The fixed wrap 34 is a wall-shaped member that protrudes from the front surface 32a (bottom surface) of the fixed end plate 32 toward the movable scroll 40. When the fixed scroll 30 is viewed from below, the fixed wrap 34 is formed in a spiral shape (involute shape) from near the center of the fixed end plate 32 toward the outer circumference. The peripheral edge 36 is a thick-walled cylindrical member that protrudes from the front surface 32a of the fixed end plate 32 toward the movable scroll 40. The peripheral edge 36 is arranged to surround the fixed wrap 34. An intake port 36a is formed in the peripheral edge 36. The lower end of the intake pipe 51 is connected to the intake port 36a.

[0062] The fixed-side wrap 34 of the fixed scroll 30 and the movable-side wrap 44 of the movable scroll 40, which will be described later, are combined to form a compression chamber Sc. Specifically, the fixed scroll 30 and the movable scroll 40 are combined with the front surface 32a of the fixed-side end plate 32 and the front surface 42a (top surface) of the movable-side end plate 42, which will be described later, facing each other. As a result, a compression chamber Sc is formed surrounded by the fixed-side end plate 32, the fixed-side wrap 34, the movable-side wrap 44, and the movable-side end plate 42 of the movable scroll 40, which will be described later (see Figure 2). When the movable scroll 40 rotates relative to the fixed scroll 30, the low-pressure refrigerant that flows from the suction pipe 51 through the suction port 36a into the peripheral compression chamber Sc is compressed as it moves towards the central compression chamber Sc, and its pressure increases.

[0063] Approximately at the center of the fixed end plate 32, a discharge port 33 is formed, penetrating the fixed end plate 32 in the thickness direction (vertical direction) to discharge the refrigerant compressed by the compression mechanism 20 (see Figure 2). The discharge port 33 communicates with the central (innermost) compression chamber Sc of the compression mechanism 20. Above the fixed end plate 32, a discharge valve 22 is attached to open and close the discharge port 33. When the pressure in the innermost compression chamber Sc, which the discharge port 33 communicates with, becomes greater than a predetermined value compared to the pressure in the discharge space Sa above the discharge valve 22, the discharge valve 22 opens, and the refrigerant from the innermost compression chamber Sc flows through the discharge port 33 into the discharge space Sa above the fixed end plate 32. The discharge space Sa communicates with a refrigerant passage (not shown) formed across the fixed scroll 30 and the housing 60. The refrigerant passage is a passage that connects the discharge space Sa with a first space S1 below the housing 60. The refrigerant, after being compressed by the compression mechanism 20 and flowing into the discharge space Sa, passes through the refrigerant passage and flows into the first space S1.

[0064] (2-2-2) Movable scroll 40 The movable scroll 40 mainly consists of a movable end plate 42, a movable lap 44, and a boss portion 46, as shown in Figure 2.

[0065] The movable end plate 42 is a disc-shaped member. The movable wrap 44 is a wall-shaped member that protrudes from the front surface 42a (top surface) of the movable end plate 42 toward the fixed scroll 30. When the movable scroll 40 is viewed from above, the movable wrap 44 is formed in a spiral shape (involute shape) from near the center of the movable end plate 42 toward the outer circumference. The boss portion 46 is a cylindrical member that protrudes from the back surface 42b (bottom surface) of the movable end plate 42 toward the motor 70.

[0066] During operation of the compressor 11, the movable scroll 40 is pressed against the fixed scroll 30 by the pressure of the crank chamber 55 and back pressure space 54, which will be described later, on the back surface 42b side of the movable end plate 42. By pressing the movable scroll 40 against the fixed scroll 30, leakage of refrigerant from the gap between the teeth of the fixed wrap 34 and the movable end plate 42, and from the gap between the teeth of the movable wrap 44 and the fixed end plate 32, is suppressed.

[0067] The boss portion 46 is located within the crank chamber 55, which will be described later, and is formed by the housing 60. The boss portion 46 is formed in a cylindrical shape. The boss portion 46 extends downward from the back surface 42b of the movable end plate 42. The upper part of the cylindrical boss portion 46 is closed by the movable end plate 42. The first bearing metal 47 is located in the hollow portion of the boss portion 46. The eccentric portion 84 of the crankshaft 80, which will be described later, is inserted into the hollow portion of the boss portion 46 (see Figure 2). As the crankshaft 80 is connected to the rotor 74 of the motor 70, as will be described later, when the motor 70 is operated and the rotor 74 rotates, the movable scroll 40 rotates.

[0068] Furthermore, the movable scroll 40, which is rotated by the motor 70, revolves around the fixed scroll 30 without rotating on its own axis, due to the action of the Oldham coupling 24 (see Figure 2) located on the back surface 42b of the movable scroll 40.

[0069] When the movable scroll 40 revolves around the fixed scroll 30, the gaseous refrigerant in the compression chamber Sc of the compression mechanism 20 is compressed. Specifically, when the movable scroll 40 revolves, gaseous refrigerant is drawn from the suction pipe 51 through the suction port 36a into the peripheral compression chamber Sc, and then the compression chamber Sc moves toward the center of the compression mechanism 20 (towards the center of the fixed end plate 32). As the compression chamber Sc moves toward the center of the compression mechanism 20, the volume of the compression chamber Sc decreases and the pressure inside the compression chamber Sc increases. As a result, the central compression chamber Sc has a higher pressure than the peripheral compression chamber Sc. The gaseous refrigerant, which has been compressed to a high pressure by the compression mechanism 20, is discharged from the central compression chamber Sc through the discharge port 33 formed in the fixed end plate 32 into the discharge space Sa. Specifically, when the pressure inside the discharge port 33 exceeds a predetermined pressure, the discharge valve 22 opens, and refrigerant flows from the discharge port 33 into the discharge space Sa. At this time, the high-pressure refrigerant in the discharge space Sa may flow back into the discharge port 33. The refrigerant discharged into the discharge space Sa flows into the first space S1 below the housing 60, passing through refrigerant passages (not shown) formed in the fixed scroll 30 and the housing 60.

[0070] (2-3) Housing 60 The housing 60 supports the fixed scroll 30 and the movable scroll 40. The housing 60 also supports the second bearing metal 112 that pivotally supports the crankshaft 80.

[0071] As shown in Figure 2, the housing 60 mainly includes the main body 120 and the upper bearing housing 110. Although not limited to these, the housing 60 is a cast product.

[0072] The main body portion 120 is a cylindrical part fixed to the casing 50. The upper bearing housing 110 is also formed in a cylindrical shape. The upper bearing housing 110 is positioned on the motor 70 side of the main body portion 120 in the axial direction of the crankshaft 80.

[0073] A fixed scroll 30 is fixed to the main body 120. Specifically, the fixed scroll 30 is placed on the housing 60 with the lower surface of the peripheral edge 36 of the fixed scroll 30 facing the upper surface of the housing 60, and is fixed to the housing 60 by fixing members (e.g., bolts) not shown. The housing 60 supports the fixed scroll 30 fixed to the main body 120.

[0074] Furthermore, the housing 60 supports the movable scroll 40, which is positioned between the fixed scroll 30 and the main body 120 of the housing 60. Specifically, the housing 60 supports the movable scroll 40 from below via an Oldham joint 24 located above the housing 60.

[0075] The main body portion 120 is fixed to the inner circumferential surface 50e of the cylindrical member 50a of the casing 50. Specifically, the housing 60 is press-fitted into the cylindrical member 50a of the casing 50, and the outer circumferential surface 122 of the main body portion 120 is in close contact with the inner circumferential surface 50e of the cylindrical member 50a at least partially and over its entire circumference in the axial direction of the crankshaft 80. The housing 60 is further fixed to the cylindrical member 50a of the casing 50 by welding.

[0076] As shown in Figure 2, the main body 120 has a first recess 56 positioned to be recessed in the center, and a second recess 58 positioned to surround the first recess 56. The first recess 56 surrounds the side surface of the crank chamber 55 where the boss portion 46 of the movable scroll 40 is located. The second recess 58 forms an annular back pressure space 54 on the back surface 42b side of the movable end plate 42.

[0077] During steady-state operation of the compressor 11 (when the operation of the compressor 11 is stable), the pressure in the crank chamber 55 becomes the high pressure in the refrigeration cycle. As a result, during steady-state operation of the compressor 11, the central part of the back surface 42b of the movable end plate 42 facing the crank chamber 55 is pushed toward the fixed scroll 30 by the high pressure.

[0078] When the movable scroll 40 rotates during the operation of the compressor 11, the back pressure space 54 communicates with the compression chamber Sc, which is in the process of compression, for a predetermined period of time during one rotation of the movable scroll 40, through a hole (not shown) formed in the movable end plate 42. Therefore, during steady-state operation of the compressor 11, the pressure in the back pressure space 54 becomes the intermediate pressure in the refrigeration cycle. As a result, during steady-state operation of the compressor 11, the peripheral edge of the back surface 42b of the movable end plate 42 facing the back pressure space 54 is pushed toward the fixed scroll 30 by the intermediate pressure.

[0079] The crank chamber 55 and the back pressure space 54 are separated by an annular wall portion 57 located at the boundary between the first recess 56 and the second recess 58 (see Figure 2). A seal ring (not shown) is positioned at the upper end of the wall portion 57 facing the back surface 42b of the movable end plate 42 to seal the space between the crank chamber 55 and the back pressure space 54.

[0080] The upper bearing housing 110 is formed in a cylindrical shape. Inside the cylindrical upper bearing housing 110, a second bearing metal 112 is provided to rotatably support the crankshaft 80. During operation of the compressor 11, a moment that could cause the crankshaft 80 to tip over may act on it. To allow the upper bearing housing 110 to tilt when a moment acts on the crankshaft 80, an elastic groove 115 is formed at the connection between the upper bearing housing 110 and the main body 120.

[0081] (2-4) Motor 70 The motor 70 has an annular stator 73 fixed to the inner wall surface of the cylindrical member 50a of the casing 50, and a rotor 74 arranged inside the stator 73 (see Figure 2).

[0082] The rotor 74 is rotatably housed inside the stator 73, with a small gap (not shown) between it and the stator 73. The rotor 74 is connected to the movable scroll 40 of the compression mechanism 20 via the crankshaft 80. Specifically, the rotor 74 is connected to the boss portion 46 of the movable scroll 40 via the crankshaft 80 (see Figure 2). The motor 70 rotates the rotor 74, thereby causing the movable scroll 40 to orbit.

[0083] (2-5) Crankshaft 80 The crankshaft 80 connects the rotor 74 of the motor 70 and the movable scroll 40 of the compression mechanism 20. The crankshaft 80 extends along the axial direction Aa as shown in Figure 2. In the compressor 11 of this embodiment, the axial direction Aa is the vertical direction. The crankshaft 80 transmits the driving force of the motor 70 to the movable scroll 40 of the compression mechanism 20.

[0084] The crankshaft 80 mainly consists of a main shaft 82 and an eccentric portion 84 (see Figure 2).

[0085] The main shaft 82 extends vertically from the oil reservoir space 50d to the crank chamber 55. The main shaft 82 is rotatably supported by the second bearing metal 112 of the upper bearing housing 110 and the third bearing metal 91 of the lower bearing 90, which will be described later. The main shaft 82 is also inserted into the rotor 74 of the motor 70 between the upper bearing housing 110 and the lower housing 130 of the housing 60 and connected to the rotor 74. The central axis of the main shaft 82 preferably coincides with the central axis B of the cylindrical member 50a of the casing 50. Hereafter, the central axis of the main shaft 82 may be referred to as the central axis of the crankshaft 80.

[0086] The eccentric portion 84 is located at the end of the main shaft 82 (the upper end in this embodiment). The central axis of the eccentric portion 84 is eccentric with respect to the central axis of the main shaft 82. The eccentric portion 84 is inserted into the boss portion 46 of the movable scroll 40 and is rotatably supported by the first bearing metal 47 located inside the boss portion 46.

[0087] An oil passage 86 is formed inside the crankshaft 80. The oil passage 86 has a main path 86a and a branch path (not shown). The main path 86a extends from the lower end to the upper end of the crankshaft 80 along the axial direction Aa of the crankshaft 80. The branch path extends from the main path in a direction intersecting the axial direction of the crankshaft 80. The refrigerant oil in the oil reservoir space 50d is pumped up by a pump (not shown) provided at the lower end of the crankshaft 80 and supplied through the oil passage 86 to the sliding parts between the crankshaft 80 and the first bearing metal 47, the second bearing metal 112, and the third bearing metal 91, and the sliding parts between the fixed scroll 30 and the movable scroll 40, etc.

[0088] (2-6) Lower Housing 130 The lower housing 130 mainly includes a lower bearing 90, an arm 94, and a fixing part 96. The lower housing 130 is a structure for supporting the crankshaft 80. For example, the lower bearing 90 is a cast product, and the bearing housing 92, arm 94, and fixing part 96 are integrally formed. However, it is not limited to this, and the bearing housing 92, arm 94, and fixing part 96 may each be separate components that are combined integrally to function as the lower housing 130.

[0089] The lower bearing 90 rotatably supports the crankshaft 80. The lower bearing 90 includes a third bearing metal 91 and a bearing housing 92. The bearing housing 92 is formed in a cylindrical shape. The third bearing metal 91, which rotatably supports the crankshaft 80, is housed inside the cylindrical bearing housing 92. The bearing housing 92 supports the third bearing metal 91.

[0090] The arm 94 supports the lower bearing 90. The arm 94 is a rod-shaped member. The lower housing 130 includes a plurality of arms 94. The number of arms 94 is not limited, but the lower housing 130 has three arms 94. Each arm 94 extends from the lower bearing 90 (specifically from the outer circumferential surface of the bearing housing 92) towards the casing 50 in the radial direction of the bearing housing 92 when the lower housing 130 is viewed along the axial direction Aa of the crankshaft 80. The three arms 94 are provided on the outer circumferential surface of the bearing housing 92 at roughly equal intervals (approximately 120 degrees apart) in the circumferential direction of the crankshaft 80, although this does not limit the structure.

[0091] Each arm 94 is provided with one fixing portion 96. Therefore, the lower housing 130 has the same number of fixing portions 96 as the arms 94. The inner circumference of each fixing portion 96 is connected to the end (outer end) of the corresponding arm 94. The lower housing 130 is fixed to the casing 50 by welding at the fixing portions 96.

[0092] (3) When the operating motor 70 of the compressor 11 is driven, the rotor 74 rotates, and the crankshaft 80 connected to the rotor 74 also rotates. As the crankshaft 80 rotates, the movable scroll 40 revolves around the fixed scroll 30 without rotating on its own axis due to the action of the Oldham coupling 24. The low-pressure refrigerant in the refrigeration cycle of the air conditioner 1 that flows in from the intake pipe 51 is drawn into the compression chamber Sc on the periphery side of the compression mechanism 20 via the intake port 36a. As the movable scroll 40 revolves and the volume of the compression chamber Sc decreases, the pressure in the compression chamber Sc increases. In addition, refrigerant at the intermediate pressure (pressure between low pressure and high pressure) in the refrigeration cycle of the air conditioner 1 is injected into the compression chamber Sc from the injection pipe 53 as needed during the compression process. As the refrigerant moves from the peripheral (outer) compression chamber Sc to the central (inner) compression chamber Sc, the pressure of the refrigerant increases, eventually becoming the high pressure in the refrigeration cycle of the air conditioner 1. The refrigerant compressed by the compression mechanism 20 is discharged from the discharge port 33 located near the center of the fixed end plate 32, and flows into the first space S1 through a refrigerant path (not shown) formed in the fixed scroll 30 and housing 60. The high-pressure refrigerant in the refrigeration cycle of the first space S1 is discharged from the discharge pipe 52.

[0093] (4) In the control air conditioning system 1 of the refrigerant circuit 10, the operating pressure ratio of the compressor 11 is 4.5 times or more and 6.25 times or less the compression ratio of the compression chamber Sc.

[0094] The operating pressure ratio of the compressor 11 is the ratio of the discharge pressure of the compressor 11 to the suction pressure of the compressor 11. The discharge pressure of the compressor 11 is the pressure of the refrigerant discharged from the discharge pipe 52 of the compressor 11 under normal conditions. The suction pressure of the compressor 11 is the pressure of the refrigerant drawn into the suction pipe 51 of the compressor 11 under normal conditions. Normal conditions refer to the state in which the pressure of the refrigerant discharged from the discharge port 33 of the compression mechanism 20 is higher than the pressure in the compression chamber Sc during compression.

[0095] The compression ratio of the compression chamber Sc is the design volume ratio, which is the ratio of the suction volume to the discharge volume of the compressor 11. The suction volume of the compressor 11 is the volume of the compression chamber Sc immediately after it is sealed off from the first space S1. In other words, the suction volume is the volume of the peripheral compression chamber Sc immediately after the refrigerant has finished flowing into the peripheral compression chamber Sc from the first space S1. The discharge volume of the compressor 11 is the volume of the compression chamber Sc when the central part of the involute shape of the fixed-side wrap 34 and the central part of the involute shape of the movable-side wrap 44 are engaged. In other words, the discharge volume is the volume of the central compression chamber Sc immediately before the compressed refrigerant is discharged from the central compression chamber Sc into the discharge space Sa. The compression ratio of the compression chamber Sc is the catalog specification of the compressor 11.

[0096] The outdoor unit control unit 71 controls the system so that the first ratio, which is the ratio of the flow rate of refrigerant flowing through the injection pipe 53 to the flow rate of refrigerant circulating in the refrigerant circuit 10, is 79% or higher. The flow rate of refrigerant flowing through the injection pipe 53 is the flow rate of the second refrigerant flowing through the second heat exchange unit 27b. The flow rate of refrigerant circulating in the refrigerant circuit 10 is the flow rate of the first refrigerant flowing through the first heat exchange unit 27a. In other words, the first ratio is the value obtained by dividing the flow rate of refrigerant flowing through the fourth pipe 64 by the flow rate of refrigerant flowing through the second pipe 62. To put it another way, the first ratio is the value obtained by dividing the flow rate of the intermediate-pressure refrigerant injected into the compression chamber Sc of the compressor 11 by the flow rate of the low-pressure refrigerant flowing into the first space S1 of the compressor 11.

[0097] The outdoor unit control unit 71 controls the first ratio by adjusting at least one of the refrigerant flow rate in the high-pressure region of the refrigerant circuit 10 and the refrigerant flow rate in the low-pressure region of the refrigerant circuit 10. The high-pressure region of the refrigerant circuit 10 is the region where high-pressure refrigerant exists. The high-pressure region is the region from the discharge side of the compressor 11 to the first expansion valve 9. The low-pressure region of the refrigerant circuit 10 is the region where low-pressure refrigerant exists. The low-pressure region is the region from the first expansion valve 9 to the suction side of the compressor 11. In Figure 3, the high-pressure region is shown by a solid line, and the low-pressure region is shown by a dashed line. In Figure 3, the region where intermediate-pressure refrigerant exists is shown by a dotted line.

[0098] The outdoor unit control unit 71 controls the opening degree of the second expansion valve 28 to adjust the pressure of the intermediate-pressure refrigerant before heat exchange in the second heat exchange section 27b of the intermediate heat exchanger 27 to a predetermined target pressure. The temperature of the intermediate-pressure refrigerant, whose pressure has been adjusted in the second heat exchange section 27b, is adjusted by heat exchange with the high-pressure refrigerant flowing through the first heat exchange section 27a. Therefore, the outdoor unit control unit 71 has the function of adjusting the temperature and pressure of the refrigerant flowing through the injection pipe 53 by controlling the opening degree of the second expansion valve 28. When the temperature and pressure of the refrigerant flowing through the injection pipe 53 change, the flow rate of the refrigerant flowing through the injection pipe 53 changes. Accordingly, the outdoor unit control unit 71 can adjust the first ratio by controlling the opening degree of the second expansion valve 28. For example, the outdoor unit control unit 71 increases the flow rate of the refrigerant flowing through the injection pipe 53 by increasing the opening degree of the second expansion valve 28, thereby increasing the first ratio. Furthermore, the outdoor unit control unit 71 controls the first ratio by reducing the flow rate of refrigerant through the injection pipe 53 by lowering the opening degree of the second expansion valve 28.

[0099] (5) Features (5-1) Conventionally, in air conditioning systems that use a vapor compression type refrigeration cycle, the operating pressure ratio, which is the catalog specification of the compressor, is about 2.0 to 4.0, regardless of the refrigerant used and the application. When a refrigeration system is equipped with a scroll compressor, in order to ensure performance at that operating pressure ratio, the design volume ratio obtained from the involute shape of the fixed scroll and movable scroll is also generally set to about 2.0 to 4.0.

[0100] Conventionally, air conditioning systems using R410A or R32 as refrigerants are known. For example, in an air conditioning system where R32 refrigerant circulates in the refrigerant circuit, the maximum operating pressure ratio is approximately 17.3 under conditions where the refrigerant condensation temperature (high-pressure side temperature) is 49°C and the refrigerant evaporation temperature (low-pressure side temperature) is -40°C. However, hot water heating products, which are a type of air conditioning system, have a need to generate high-temperature water when the outside air temperature is low. In such cases, it is necessary to operate the hot water heating product under conditions of a higher condensation temperature and a lower evaporation temperature than conventional air conditioning systems. Therefore, there is a need for an air conditioning system that can operate at a higher operating pressure ratio than conventional air conditioning systems.

[0101] However, if the operating pressure ratio to the design volume ratio of the scroll compressor is set too high, the flow rate of refrigerant flowing back from the high-pressure region of the refrigerant circuit into the compression chamber will increase when the discharge port of the fixed scroll opens. When refrigerant from the high-pressure region flows back into the compression chamber, an impact load is applied to the crankshaft bearing. If the thickness of the refrigerant oil covering the bearing decreases instantaneously when an impact load is applied, the bearing may be damaged.

[0102] (5-2) In the air conditioning system 1, the refrigerant circuit 10 is filled with a refrigerant for performing a vapor compression type refrigeration cycle. The refrigerant filled in the refrigerant circuit 10 is a refrigerant that requires operation under conditions where the operating pressure ratio of the compressor 11 is higher than when R410A and R32 are used as refrigerants. For example, the refrigerants filled in the refrigerant circuit 10 are R454C and R290. In the air conditioning system 1, the operating pressure ratio of the compressor 11 is 4.5 times or more and 6.25 times or less the compression ratio of the compression chamber Sc.

[0103] The outdoor unit control unit 71 controls the system so that the first ratio is 79% or higher, supplying intermediate-pressure refrigerant to the compression chamber Sc from the injection pipe 53 while the refrigerant is being compressed in the compression chamber Sc. As a result, the pressure in the compression chamber Sc communicating with the discharge port 33 rises before the discharge port 33 opens and refrigerant flows back into the compression chamber Sc from the high-pressure region (discharge space Sa) of the refrigerant circuit 10. Consequently, the impact load applied to the bearing portion of the crankshaft 80 is reduced by the refrigerant flowing back into the compression chamber Sc when the discharge port 33 opens. The bearing portion of the crankshaft 80 refers to the sliding portion between the crankshaft 80 and the first bearing metal 47, the sliding portion between the crankshaft 80 and the second bearing metal 112, and the sliding portion between the crankshaft 80 and the third bearing metal 91.

[0104] The threshold for the first ratio (79%) is set based on the measured surface roughness (Ra, etc.) of the bearing portion of the crankshaft 80 after an endurance test in which the compressor 11 is operated continuously for a long period of time at a high operating pressure ratio. The surface roughness is measured for the first bearing metal 47, the second bearing metal 112, and the third bearing metal 91. If the surface roughness after the endurance test is above a predetermined threshold, it is determined that there is a risk of damage to the bearing portion due to impact load. In this embodiment, it was confirmed that when the outdoor unit control unit 71 performs control in which the first ratio is less than 79%, there is a risk of damage to at least one of the second bearing metal 112 and the third bearing metal 91 due to impact load. Furthermore, it was confirmed that when the outdoor unit control unit 71 performs control in which the first ratio is 79% or more, there is no risk of damage to the first bearing metal 47, the second bearing metal 112, and the third bearing metal 91 due to impact load.

[0105] The conditions for conducting the durability test of the compressor 11 described above are as follows: ・Refrigerant filled in the refrigerant circuit 10: R454C ・Refrigerant oil filled in the refrigerant circuit 10: FVC56EA (Daphne Hermetic Oil FVC-EA series manufactured by Idemitsu Kosan Co., Ltd.) ・Condensing temperature: 75℃ ・Evaporation temperature: -32℃ ・Rotation speed of compressor 11: 50 rpm ・Continuous operation time of compressor 11: 400 hours The minimum value of the impact load at which at least one of the first bearing metal 47, the second bearing metal 112, and the third bearing metal 91 is damaged is called the maximum allowable impact load. Figure 4 shows a schematic relationship between the first ratio controlled by the outdoor unit control unit 71 and the impact load applied to the bearing portion of the crankshaft 80. In Figure 4, the "first ratio" on the horizontal axis corresponds to the flow rate of the intermediate-pressure refrigerant in the injection pipe 53. In Figure 4, the "impact load" on the vertical axis represents the impact load applied to the bearing portion of the crankshaft 80 by the refrigerant flowing back into the compression chamber Sc. Line M1 shows the change in the first impact load due to the inflow of intermediate-pressure refrigerant from the injection pipe 53 into the compression chamber Sc. Line M2 shows the change in the second impact load due to the backflow of high-pressure refrigerant from the discharge space Sa into the compression chamber Sc. As shown by line M1, the first impact load increases as the first ratio increases. As shown by line M2, the second impact load decreases as the first ratio increases. When the first ratio is 79% or higher, the second impact load is less than or equal to the maximum allowable impact load.

[0106] Therefore, even when the air conditioning system 1 is required to operate under conditions where the operating pressure ratio of the compressor 11 is higher than that of a conventional air conditioning system, it reduces the impact load applied to the bearing portion of the crankshaft 80 and suppresses damage to the bearing portion of the crankshaft 80.

[0107] (5-3) High-pressure refrigerants such as R410A and R32 have a higher pressure after being compressed by the compressor when used in a refrigeration system compared with low-pressure refrigerants such as R454C and R290. Therefore, when a refrigeration system equipped with a scroll compressor uses a high-pressure refrigerant, the bearing stress applied to the crankshaft tends to increase due to the radial and tangential gas loads caused by the pressure of the refrigerant in the compression chamber. Radial gas load is a load that acts in the opposite direction to the eccentric direction of the movable scroll 40 due to the gas load (the load exerted on the movable side wrap 44 by the pressure of the gas refrigerant in the compression chamber). Tangential gas load is a load that acts in the opposite direction to the direction of travel of the movable scroll 40 (tangential direction of rotational motion) due to the gas load. The tangential gas load acts in a direction perpendicular to the radial gas load. When using a high-pressure refrigerant, if an intermediate-pressure refrigerant is injected into the compression chamber, the pressure in the compression chamber increases, increasing the radial and tangential gas loads, and thus further increasing the bearing stress. Therefore, in refrigeration systems that use high-pressure refrigerants, an upper limit is set for the ratio (first ratio) between the flow rate of the injected refrigerant and the flow rate of the refrigerant circulating in the refrigerant circuit. For example, in refrigeration systems that use R32 as a refrigerant, the first ratio is limited to approximately 16% or less because the pressure of the compressed refrigerant is high.

[0108] On the other hand, in an air conditioning system 1 where low-pressure refrigerant is used to fill the refrigerant circuit 10, the pressure of the refrigerant compressed in the compression chamber Sc is lower compared to when high-pressure refrigerant is used, and the radial and tangential gas loads are smaller, resulting in less bearing stress due to the pressure of the compressed refrigerant. Therefore, in the air conditioning system 1, it is possible to increase the flow rate of the injected refrigerant to increase the first ratio.

[0109] Specifically, the outdoor unit control unit 71 can perform control such that the first ratio is 79% or higher. As a result, the air conditioning system 1 can inject refrigerant at intermediate pressure into the compression chamber Sc, thereby reducing the impact load applied to the bearing portion of the crankshaft 80 as described above. The reason for the reduction in impact load will be explained with reference to Figure 5.

[0110] In Figure 5, the horizontal axis, "crank angle," represents the rotation angle of the movable scroll 40. As the movable scroll 40 rotates relative to the fixed scroll 30, the crank angle increases in the order of A1, A2, and A3. In Figure 5, the vertical axis, "vortex internal pressure," is the pressure exerted by the refrigerant in the compression chamber Sc on the fixed-side wrap 34 and the movable-side wrap 44.

[0111] Figure 5 shows graphs schematically representing the change in vortex pressure for both "with INJ" and "without INJ". In Figure 5, the graph for "with INJ" is shown as a solid line, and the graph for "without INJ" is shown as a dashed line. The graph for "with INJ" represents the change in vortex pressure in this embodiment. The graph for "with INJ" represents the change in vortex pressure when intermediate-pressure refrigerant is supplied from the injection pipe 53 to the compression chamber Sc during the operation of the compressor 11. The graph for "without INJ" represents the change in vortex pressure as a comparative example. The graph for "without INJ" represents the change in vortex pressure when intermediate-pressure refrigerant is not supplied from the injection pipe 53 to the compression chamber Sc during the operation of the compressor 11. The graph for "with INJ" represents the change when the opening of the second expansion valve 28 is greater than zero. The graph for "without INJ" represents the change when the opening of the second expansion valve 28 is zero.

[0112] First, let's explain the graph without INJ.

[0113] The crank angle A1 is the angle immediately after the peripheral compression chamber Sc is closed off from the first space S1, following the inflow of low-pressure refrigerant from the first space S1 into the peripheral compression chamber Sc. At crank angle A1, low-pressure refrigerant is present in the peripheral compression chamber Sc. At crank angle A1, the internal pressure of the vortex is P1.

[0114] As the crank angle increases from A1 to A3, the peripheral compression chamber Sc, which was sealed off from the first space S1 when the crank angle was A1, gradually moves towards the center, becoming the central compression chamber Sc when the crank angle is A3. During this time, the volume of the compression chamber Sc decreases, and the low-pressure refrigerant present in the peripheral compression chamber Sc is compressed. As a result, high-pressure refrigerant is present in the central compression chamber Sc when the crank angle is A3. As the crank angle increases from A1 to A3, the pressure in the compression chamber Sc increases, causing the vortex pressure to rise from P1 to P3.

[0115] The crank angle A3 is the angle at which the discharge port 33 opens. At crank angle A3, the high-pressure refrigerant in the discharge space Sa passes through the discharge port 33 and begins to flow back into the central compression chamber Sc. As a result, after the crank angle reaches A3, the internal pressure of the vortex rises from P3 to P5 in a short time. The difference between the internal pressure of the vortex P3 and the internal pressure of the vortex P5 corresponds to the impact load L1 applied to the bearing portion of the crankshaft 80 in the graph for the "no INJ" case.

[0116] Next, I will explain the graph with "INJ enabled".

[0117] The crank angle A1 is the angle immediately after the peripheral compression chamber Sc is closed off from the first space S1, following the inflow of low-pressure refrigerant from the first space S1 into the peripheral compression chamber Sc. At crank angle A1, low-pressure refrigerant is present in the peripheral compression chamber Sc. At crank angle A1, the internal pressure of the vortex is P1. At crank angle A1, the injection pipe 53 begins communication with the peripheral compression chamber Sc.

[0118] As the crank angle increases from A1 to A2, the volume of the peripheral compression chamber Sc, which is sealed off from the first space S1 when the crank angle is A1, decreases, and the refrigerant in the compression chamber Sc is compressed. During this time, refrigerant at an intermediate pressure is supplied to the peripheral compression chamber Sc from the injection pipe 53.

[0119] The crank angle A2 is the angle at which the injection pipe 53 terminates communication with the compression chamber Sc. As the crank angle increases from A1 to A2, the pressure in the compression chamber Sc increases, causing the vortex pressure to rise from P1 to P2. Since refrigerant is supplied to the compression chamber Sc from the injection pipe 53, the vortex pressure P2 in the graph with injection at crank angle A2 is greater than the vortex pressure P2' in the graph without injection at crank angle A2.

[0120] As the crank angle increases from A2 to A3, the compression chamber Sc gradually moves towards the center, becoming the central compression chamber Sc when the crank angle is A3. During the increase in the crank angle from A2 to A3, no refrigerant is supplied to the compression chamber Sc from the injection pipe 53. During this time, the volume of the compression chamber Sc decreases, and the refrigerant in the compression chamber Sc is compressed. As a result, high-pressure refrigerant is present in the central compression chamber Sc when the crank angle is A3. As the crank angle increases from A2 to A3, the pressure in the compression chamber Sc increases, causing the vortex pressure to rise from P2 to P4. At crank angle A2, the vortex pressure P2 is higher than the vortex pressure P2', so the vortex pressure P4 is higher than the vortex pressure P3.

[0121] The crank angle A3 is the angle at which the discharge port 33 opens. At crank angle A3, the high-pressure refrigerant in the discharge space Sa passes through the discharge port 33 and begins to flow back into the central compression chamber Sc. As a result, after the crank angle reaches A3, the internal pressure of the vortex rises from P4 to P5 in a short time. The difference between the internal pressure of the vortex P4 and the internal pressure of the vortex P5 corresponds to the impact load L2 applied to the bearing portion of the crankshaft 80 in the graph for the "with INJ" configuration.

[0122] The pressure of the high-pressure refrigerant in the discharge space Sa is approximately the same in both the "with INJ" and "without INJ" cases. Therefore, in both the "with INJ" and "without INJ" graphs, after the crank angle reaches A3, the vortex internal pressure increases to approximately the same value P5.

[0123] As shown in Figure 5, the impact load L2 in the graph with INJ is smaller than the impact load L2 in the graph without INJ. The difference in impact load L1-L2 corresponds to the difference between the internal spiral pressure P4 and the internal spiral pressure P3.

[0124] By the outdoor unit control unit 71 performing control such that the first ratio is 79% or higher, the impact load applied to the bearing portion of the crankshaft 80 is reduced by a minimum of 4.2% and a maximum of 20.5%. In other words, in Figure 5, (L1 - L2) / L1, which represents the degree of impact load reduction, is between 4.2% and 20.5%.

[0125] Therefore, in the air conditioning system 1, when using a low-pressure refrigerant such as R454C, which has a lower pressure after compression compared to high-pressure refrigerants such as R410A and R32, a large amount of intermediate-pressure refrigerant is injected into the compression chamber Sc, thereby suppressing a rapid increase in the pressure of the compression chamber Sc when communicating with the discharge port 33. As a result, the air conditioning system 1 can reduce the impact load applied to the bearing portion of the crankshaft 80, thereby suppressing damage to the bearing portion of the crankshaft 80, compared to when intermediate-pressure refrigerant is not injected.

[0126] (5-4) The outdoor unit control unit 71 can be operated under conditions of a higher condensation temperature and a lower evaporation temperature than conventional air conditioning systems by increasing the first ratio and increasing the flow rate of the intermediate-pressure refrigerant injected into the compression chamber Sc. Therefore, for example, if the air conditioning system 1 is a hot water heating product, the air conditioning system 1 can ensure sufficient capacity to generate high-temperature water under conditions where the outside air temperature is low. Consequently, the air conditioning system 1 has the effect of improving energy efficiency.

[0127] (6) Modified Examples (6-1) Modified Example A In the air conditioning system 1, the operating pressure ratio of the compressor 11 is 4.5 times or more and 6.25 times or less the compression ratio of the compression chamber Sc. The operating pressure ratio of the compressor 11 and the compression ratio of the compression chamber Sc may be set as appropriate. For example, the operating pressure ratio of the compressor 11 may be set to 18 or more and 25 or less. The compression ratio of the compression chamber Sc may be set to 4 or less.

[0128] (6-2) Modification B The outdoor unit control unit 71 further controls the intermediate pressure refrigerant flowing through the injection pipe 53 so that it is lower than the discharge pressure of the compressor 11. If the intermediate pressure refrigerant flowing through the injection pipe 53 is higher than the discharge pressure of the compressor 11, the bearing stress caused by the intermediate pressure refrigerant injected into the compression chamber Sc tends to be large. Therefore, the air conditioning system 1 can reduce the impact load applied to the crankshaft 80 due to bearing stress and suppress damage to the bearing portion of the crankshaft 80.

[0129] (6-3) Modification C The outdoor unit control unit 71 may further control the first ratio to be 381% or less. If the first ratio becomes too high, the pressure in the compression chamber Sc that compresses the refrigerant will increase, and the bearing stress will increase. By setting an upper limit for the first ratio, the air conditioner 1 can reduce the impact load applied to the crankshaft 80 due to bearing stress and suppress damage to the bearing portion of the crankshaft 80.

[0130] (6-4) Modification D The compressor 11 of the embodiment may be a type of compressor other than a scroll compressor, as long as it has the function of injecting a refrigerant at an intermediate pressure into the compression chamber. For example, the compressor 11 may be a rotary compressor.

[0131] While embodiments of this disclosure have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of this disclosure as described in the claims.

[0132] 1: Air conditioning system (refrigeration system) 10: Refrigerant circuit 11: Compressor 28: Second expansion valve (expansion valve) 30: Fixed scroll 40: Movable scroll 53: Injection pipe (injection passage) 64: Fourth piping (piping) 71: Outdoor unit control unit (control unit) Sc: Compression chamber

[0133] Japanese Patent Publication No. 2018-184872

Claims

1. A refrigeration system (1) comprising: a compressor (11) and a refrigerant circuit (10) that circulates a refrigerant by the compressor to perform a refrigeration cycle; and a control unit (71) that performs control related to the refrigeration cycle, wherein the compressor has a compression chamber (Sc) in which the refrigerant is compressed and an injection passage (53) communicating with the compression chamber, the ratio of the discharge pressure to the suction pressure of the compressor is 4.5 times or more and 6.25 times or less the compression ratio of the compression chamber, and the control unit performs control such that the first ratio, which is the ratio of the flow rate of the refrigerant flowing through the injection passage to the flow rate of the refrigerant circulating through the refrigerant circuit, is 79% or more.

2. The refrigeration apparatus according to claim 1, wherein the control unit further controls the refrigerant flowing through the injection passage to be lower than the discharge pressure.

3. The refrigeration apparatus according to claim 1 or 2, wherein the control unit further performs control such that the first ratio is 381% or less.

4. The refrigeration apparatus according to any one of claims 1 to 3, wherein the ratio of the discharge pressure to the suction pressure is 18 or more and 25 or less, and the compression ratio is 4 or less.

5. The refrigeration apparatus according to any one of claims 1 to 4, wherein the compressor comprises a fixed scroll (30) and a movable scroll (40) that together with the fixed scroll form the compression chamber, and the injection passage is formed in the fixed scroll.

6. The refrigeration apparatus according to any one of claims 1 to 5, wherein the refrigerant is R454C or R290.

7. The refrigeration apparatus according to any one of claims 1 to 6, wherein the control unit controls the first ratio by adjusting at least one of the flow rate of refrigerant in the high-pressure region of the refrigerant circuit and the flow rate of refrigerant in the low-pressure region of the refrigerant circuit.

8. The refrigeration apparatus according to any one of claims 1 to 7, wherein the refrigerant circuit further comprises: an expansion valve (28) that reduces the pressure of the high-pressure refrigerant in the refrigeration cycle until it becomes an intermediate-pressure refrigerant; and a pipe (64) through which the intermediate-pressure refrigerant flows and which is connected to the injection passage, and the control unit controls the opening degree of the expansion valve to adjust the first ratio.

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