Refrigeration cycle device

Abstract

A refrigeration cycle device is provided with: a compressor (11) that sucks in refrigerant and discharges the refrigerant after compressing it; a heat releasing portion (12) that causes the refrigerant to release heat; a pressure reducing portion (14) that reduces the pressure of the refrigerant and is able to adjust the flow path opening degree to adjust the flow rate of the refrigerant; an evaporating portion (15) that causes the refrigerant reduced in pressure in the pressure reducing portion to absorb heat from air; a refrigerant state detecting portion (64, 66) that detects the state of the refrigerant at a position downstream of the refrigerant inlet of the evaporating portion and upstream of the suction inlet of the compressor; and a control portion (60) that controls the opening degree of the pressure reducing portion to a normal opening degree (EVN) that makes the superheat degree (SHE) of the refrigerant flowing out from the evaporator close to a target superheat degree (SHEO), and that determines whether the refrigerant is dry in the evaporating portion based on the state of the refrigerant detected by the refrigerant state detecting portion, and sets the opening degree of the pressure reducing portion to be greater than the normal opening degree in the case where it is determined that the refrigerant is dry in the evaporating portion.

Description

[0001] Cross-referencing of related applications

[0002] This application is based on Japanese Patent Application No. 2020-140048, filed on August 21, 2020, and Japanese Patent Application No. 2021-87579, filed on May 25, 2021, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a refrigeration cycle device that controls the opening degree of the pressure reducing unit through a control unit. Background Technology

[0004] Previously, Patent Document 1 described a refrigeration cycle device suitable for an air conditioning unit in a vehicle. In this prior art, the evaporator cools the air blown into the vehicle interior by exchanging heat between the refrigerant flowing out from the expansion valve and the air blown into the vehicle interior.

[0005] The opening degree of the expansion valve is controlled by a control device to ensure that the superheat of the refrigerant flowing into the compressor is close to the target superheat.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2019-26111

[0009] According to the aforementioned existing technology, there are situations where the evaporator's intake air temperature is low, preventing the refrigerant flowing into the compressor from achieving superheat. Under such conditions, with large load fluctuations, the refrigerant dries out in the evaporator, thus preventing the evaporator from fulfilling its cooling capacity. "Drying out" refers to excessive evaporation of the refrigerant in the evaporator, resulting in an excessively large area where only gaseous refrigerant exists. Summary of the Invention

[0010] In view of the above points, the present invention aims to suppress the drying of refrigerant in the evaporator.

[0011] A refrigeration cycle apparatus according to one aspect of the present invention includes: a compressor, a heat dissipation section, a pressure reduction section, an evaporation section, a refrigerant status detection section, and a control section.

[0012] The compressor draws in refrigerant, compresses it, and then discharges it. The heat release section causes the refrigerant to release heat. The pressure reducing section reduces the pressure of the refrigerant and can adjust the flow path opening to regulate the refrigerant flow rate. The evaporation section allows the refrigerant, after being depressurized in the pressure reducing section, to absorb heat from the air. The refrigerant condition detection section detects the condition of the refrigerant located downstream of the refrigerant inlet in the evaporation section and upstream of the compressor's suction inlet.

[0013] The control unit controls the opening of the pressure reducing section to a normal opening, which is the opening that makes the superheat of the refrigerant flowing out of the evaporator close to the target superheat. The control unit determines whether the refrigerant in the evaporator is dry based on the state of the refrigerant detected by the refrigerant state detection unit. If it is determined that the refrigerant in the evaporator is dry, the control unit sets the opening of the pressure reducing section to be greater than the normal opening.

[0014] Therefore, it is possible to properly determine whether the refrigerant in the evaporator is dry. Furthermore, if it is determined that the refrigerant in the evaporator is dry, the flow rate of the refrigerant flowing into the evaporator can be increased, thereby suppressing the drying of the refrigerant in the evaporator.

[0015] The above-mentioned and other objects, features, and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is an overall structural diagram of the refrigeration cycle device in the first embodiment.

[0017] Figure 2 This is a block diagram showing the electrical control unit of the refrigeration cycle device in the first embodiment.

[0018] Figure 3 This is a flowchart illustrating the control processing of the control program in the first embodiment.

[0019] Figure 4 It is a graph showing the refrigerant temperature and refrigerant pressure when no drying occurs in the evaporator of the first embodiment.

[0020] Figure 5 It is a graph showing the refrigerant temperature and refrigerant pressure when drying occurs in the evaporator of the first embodiment.

[0021] Figure 6 It is a graph showing the refrigerant temperature and refrigerant pressure when the refrigerant flow rate is high in the evaporator of the first embodiment.

[0022] Figure 7 It is a graph showing the refrigerant temperature and refrigerant pressure when the intake air temperature is low in the evaporator of the first embodiment.

[0023] Figure 8 It is a graph showing the operation of the expansion valve when the intake air temperature is low in the evaporator of the first embodiment.

[0024] Figure 9 This is a flowchart illustrating the control processing of the control program in the second embodiment.

[0025] Figure 10 This is the control characteristic diagram used in the control processing of the control program in the second embodiment. Detailed Implementation

[0026] Hereinafter, various embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In each embodiment, the same reference numerals may be used to denote parts corresponding to matters described in previous embodiments, and repeated descriptions may be omitted. In cases where only a portion of the structure is described in each embodiment, other parts of the structure can be described using other embodiments described previously. Except for the combinations of parts that are explicitly shown to be specifically combinable in each embodiment, embodiments can be partially combined with each other even without explicit description, provided there are no particular obstacles to the combination.

[0027] (First Implementation)

[0028] The first embodiment will now be described with reference to the accompanying drawings. Figure 1 The vehicle air conditioning unit shown is an air conditioning unit that adjusts the interior space of a car (in other words, the space to be conditioned) to a suitable temperature. The vehicle air conditioning unit has a refrigeration circulation device 10.

[0029] The refrigeration cycle device 10 is a vapor compression refrigeration machine equipped with a compressor 11, a condenser 12, a receiver 13, an expansion valve 14, and an evaporator 15. In the refrigeration cycle device 10 of this embodiment, a Freon-based refrigerant is used as the refrigerant, and a subcritical refrigeration cycle is formed in which the refrigerant pressure on the high-pressure side does not exceed the critical pressure of the refrigerant.

[0030] A refrigerant circulation loop is formed in the refrigeration cycle device 10. In the refrigerant circulation loop, the refrigerant circulates in the order of compressor 11, condenser 12, receiver 13, expansion valve 14, evaporator 15, and compressor 11.

[0031] Compressor 11 is an electric compressor driven by electricity supplied from a battery. It draws in refrigerant from the refrigeration cycle unit 10, compresses it, and then discharges it. The motor of compressor 11 is... Figure 2 The control device 60 shown controls the compressor 11. The compressor 11 can also be a variable capacity compressor that is driven by a motor.

[0032] The condenser 12 is a high-pressure side heat exchanger that condenses the high-pressure side refrigerant discharged from the compressor 11 by releasing heat. The condenser 12 condenses the high-pressure side refrigerant by exchanging heat between the high-pressure side refrigerant discharged from the compressor 11 and the outside air. The condenser 12 can also condense the high-pressure side refrigerant by exchanging heat between the high-pressure side refrigerant discharged from the compressor 11 and cooling water.

[0033] Receiver 13 is a gas-liquid separation section that separates the high-pressure refrigerant gas from the condenser 12, allowing the separated liquid refrigerant to flow downstream, and storing the remaining refrigerant in circulation.

[0034] Expansion valve 14 is a pressure-reducing section that causes the liquid refrigerant flowing from receiver 13 to expand under reduced pressure. Expansion valve 14 is an electric expansion valve. An electric expansion valve is an electrical variable throttling mechanism configured to have a valve core capable of changing the throttling opening and an electric actuator that changes the opening of the valve core.

[0035] Expansion valve 14 is a refrigerant flow switching unit that switches between the state where refrigerant flows in evaporator 15 and the state where no refrigerant flows. The operation of expansion valve 14 is controlled by a control signal output from control device 60.

[0036] Evaporator 15 is an evaporator that causes the refrigerant flowing out of expansion valve 14 to evaporate by exchanging heat with the air blown into the vehicle interior. In evaporator 15, the refrigerant absorbs heat from the air blown into the vehicle interior. Evaporator 15 is an air cooler that cools the air blown into the vehicle interior. The gaseous refrigerant evaporated in evaporator 15 is drawn into compressor 11 and compressed.

[0037] The evaporator 15 is housed in the air conditioning housing 51 of the interior air conditioning unit 50. The interior air conditioning unit 50 is located inside an instrument panel (not shown) at the front of the vehicle interior. The air conditioning housing 51 is an air passage forming component that forms an air passage.

[0038] The air conditioner housing 51 is equipped with an indoor / outdoor air switching box 52, an indoor air supply fan 53, and a heater core 54. The indoor / outdoor air switching box 52 is an air switching unit that switches the introduction of indoor and outdoor air into the air passage within the air conditioner housing 51. The indoor air supply fan 53 draws in and blows in the indoor and outdoor air introduced into the air passage within the air conditioner housing 51 through the indoor / outdoor air switching box 52. The operation of the indoor air supply fan 53 is controlled by a control device 60.

[0039] The heater core 54 is disposed downstream of the airflow from the evaporator 15 in the air passage within the air conditioning housing 51. The heater core 54 is an air heater that heats the air blown into the vehicle interior by exchanging heat between high-temperature cooling water and the air being blown into the vehicle interior. The high-temperature cooling water is heated by a heat source such as a running engine or an electric heater. Alternatively, the high-temperature cooling water may be heated by the condenser 12.

[0040] An air mixing gate 55 is provided between the evaporator 15 and the heater core 54 in the air passage within the air conditioner housing 51. The air mixing gate 55 adjusts the airflow ratio between the cold air flowing into the heater core 54 from the cold air passing through the evaporator 15 and the cold air flowing in the cold air bypass passage 56.

[0041] The cold air bypass passage 56 is an air passage through which cold air passing through the evaporator 15 flows around the heater core 54. The rotation shaft of the air mixing door 55 is driven by the air mixing door servo motor 57. The operation of the air mixing door servo motor is controlled by the control device 60.

[0042] The air mixing door 55 can be a sliding door that slides in a direction approximately orthogonal to the airflow. The sliding door can be a plate-shaped door formed of a rigid body, or a membrane door formed of a flexible thin-film material.

[0043] Air conditioning air, whose temperature has been adjusted by the air mixing door 55, is blown into the vehicle interior from the outlet 58 formed in the air conditioning housing 51.

[0044] Figure 2 The control device 60 shown is composed of a known microcomputer including a CPU, ROM, and RAM, and its peripheral circuitry. The control device 60 performs various calculations and processes based on a control program stored in the ROM. Various controlled devices are connected to the output side of the control device 60. The control device 60 is a control unit that controls the operation of various controlled devices.

[0045] The controlled devices controlled by the control device 60 include the compressor 11, expansion valve 14, indoor air supply fan 53, and servo motor 57 for air mixing door, etc.

[0046] The software and hardware in the control device 60 that control the motor of the compressor 11 constitute a refrigerant discharge capacity control unit. The software and hardware in the control device 60 that control the expansion valve 14 constitute a throttling control unit.

[0047] The software and hardware of the control room fan 53 in the control device 60 constitute an air supply capacity control unit. The software and hardware of the servo motor 57 for controlling the air mixing door in the control device 60 constitute an air volume proportional control unit.

[0048] Various control sensor groups are connected to the input side of the control device 60. These control sensor groups include an internal air temperature sensor 61, an external air temperature sensor 62, a solar radiation sensor 63, an evaporator temperature sensor 64, a refrigerant intake temperature sensor 65, a refrigerant intake pressure sensor 66, and a high-temperature cooling water temperature sensor 67.

[0049] Interior air temperature sensor 61 detects the vehicle interior temperature Tr. Exterior air temperature sensor 62 detects the exterior air temperature Tam. Solar radiation sensor 63 detects the solar radiation inside the vehicle interior Ts.

[0050] Evaporator temperature sensor 64 is an evaporator temperature detection unit that detects the refrigerant evaporation temperature (evaporator temperature) in evaporator 15. Specifically, evaporator temperature sensor 64 detects the temperature of the heat exchange fins of evaporator 15.

[0051] The evaporator temperature sensor 64 is disposed in the region of the evaporator 15 where liquid refrigerant exists when it is not drying. For example, the evaporator temperature sensor 64 is disposed on the upstream side of the refrigerant flow in the evaporator 15.

[0052] The intake refrigerant temperature sensor 65 is an intake refrigerant temperature detection unit that detects the intake refrigerant temperature Tsuc of the refrigerant drawn into the compressor 11. In other words, the intake refrigerant temperature sensor 65 detects the temperature of the refrigerant on the outlet side of the evaporator 15.

[0053] The suction refrigerant pressure sensor 66 is a suction refrigerant temperature detection unit that detects the suction refrigerant pressure Psuc of the refrigerant drawn into the compressor 11. In other words, the suction refrigerant pressure sensor 66 detects the pressure of the refrigerant on the outlet side of the evaporator 15.

[0054] The intake refrigerant temperature sensor 65 and the intake refrigerant pressure sensor 66 are disposed in the area where superheated refrigerant exists when no drying occurs in the evaporator 15. For example, the intake refrigerant temperature sensor 65 and the intake refrigerant pressure sensor 66 are disposed in the refrigerant piping between the evaporator 15 and the compressor 11.

[0055] The evaporator temperature sensor 64 and the suction refrigerant pressure sensor 66 are refrigerant state detection units that detect the state of the refrigerant at a location downstream of the refrigerant inlet of the expansion valve 14 and upstream of the suction inlet of the compressor 11. More preferably, the evaporator temperature sensor 64 and the suction refrigerant pressure sensor 66 detect the state of the refrigerant at a location downstream of the refrigerant inlet of the evaporator 15 and upstream of the suction inlet of the compressor 11.

[0056] The refrigerant pressure sensor 66 is a first detection unit that detects the state of the refrigerant at a location downstream of the outlet of the evaporator 15 and upstream of the inlet of the compressor 11. The evaporator temperature sensor 64 is a second detection unit that detects the state of the refrigerant at a location downstream of the inlet of the evaporator 15 and upstream of the outlet of the evaporator 15.

[0057] The high-temperature cooling water temperature sensor 67 detects the temperature TW of the high-temperature cooling water flowing into the heater core 54. For example, the high-temperature cooling water temperature sensor 67 detects the temperature of the cooling water flowing out of the condenser 12.

[0058] Various operating switches (not shown) are connected to the input side of the control device 60. These operating switches are located on the control panel 70 and operated by the occupant. The control panel 70 is situated near the instrument panel at the front of the vehicle interior. Operating signals from the various operating switches are input to the control device 60.

[0059] The various operating switches include automatic switches, air conditioning switches, and temperature setting switches. Automatic switches are used to set and deactivate the automatic control of the vehicle's air conditioning system. Air conditioning switches determine whether the air is cooled in the interior air conditioning unit 50. Temperature setting switches are used to set the desired temperature inside the vehicle.

[0060] Next, the operation of the above structure will be explained. The following describes the operation when the automatic switch of the control panel 70 is turned on by an occupant. When the air conditioning switch on the control panel 70 is turned on by an occupant, the control device 60 executes the air conditioning control program.

[0061] In the air conditioning control program, the compressor speed Nc, the opening degree SW of the air mixing valve 55, and the throttling opening degree EV of the expansion valve 14 are determined. The compressor speed 11 is determined by feedback control based on the deviation between the target evaporator temperature TEO and the evaporator temperature Tefin detected by the evaporator temperature sensor 64, aiming to bring the evaporator temperature Tefin close to the target evaporator temperature TEO. The target evaporator temperature TEO is determined based on the target blow-out temperature TAO and with reference to the control mapping stored in the control device 60. In the control mapping of this embodiment, it is determined that the target evaporator temperature TEO increases as the target blow-out temperature TAO increases.

[0062] The target airflow temperature (TAO) is the target temperature of the air blown into the vehicle interior. The control unit 60 calculates the target airflow temperature (TAO) based on the following formula F1.

[0063] TAO=Kset×Tset-Kr×Tr-Kam×Tam-Ks×Ts+C···(F1)

[0064] In this formula, Tset is the interior set temperature set by the temperature setting switch on the operation panel 70, Tr is the interior air temperature detected by the interior air temperature sensor 61, Tam is the outside air temperature detected by the outside air temperature sensor 62, and Ts is the solar radiation detected by the solar radiation sensor 63. Kset, Kr, Kam, and Ks are control gains, and C is a constant used for calibration.

[0065] The opening degree SW of the air mixing door 55 is determined to make the air-conditioned air, after being conditioned by the air mixing door 55, reach the target outlet temperature TAO. Specifically, the opening degree of the air mixing door 55 is determined based on the target outlet temperature TAO, the evaporator temperature Tefin, and the temperature TW of the high-temperature cooling water flowing into the heater core 54.

[0066] The throttling opening EV of expansion valve 14 is through Figure 3 The control process shown in the flowchart determines the value. First, in step S100, the throttling opening EVN of the expansion valve 14 during normal control (hereinafter referred to as the normal opening) is determined by feedback control based on the deviation between the target superheat SHEO of the refrigerant at the outlet side of the evaporator 15 and the superheat SHE of the refrigerant at the outlet side of the evaporator 15. This aims to bring the superheat SHE close to the target superheat SHEO. For example, the target superheat SHEO is a preset constant (5°C in this embodiment).

[0067] The superheat SHE is calculated based on the intake refrigerant pressure Psuc detected by the intake refrigerant pressure sensor 66 and the intake refrigerant temperature Tsuc detected by the intake refrigerant temperature sensor 65.

[0068] In the next step S110, it is determined whether the temperature difference obtained by subtracting the evaporator outlet saturation temperature Tsat from the evaporator temperature Tefin exceeds a threshold α1. The evaporator outlet saturation temperature Tsat is calculated based on the suction refrigerant pressure Psuc detected by the suction refrigerant pressure sensor 66. The threshold α1 is a positive value appropriately determined by the control device 60.

[0069] If the temperature difference between the evaporator temperature Tefin and the evaporator outlet saturation temperature Tsat does not exceed the threshold α1, it is considered that no drying has occurred in the evaporator 15. If the temperature difference between the evaporator temperature Tefin and the evaporator outlet saturation temperature Tsat exceeds the threshold α1, it is considered that drying has occurred in the evaporator 15.

[0070] That is, such as Figure 4 As shown, when no drying occurs in the evaporator 15, the evaporator temperature sensor 64 detects the temperature of the refrigerant that does not have superheat. Therefore, the temperature difference obtained by subtracting the evaporator outlet saturation temperature Tsat from the evaporator temperature Tefin is lower than the threshold α1.

[0071] like Figure 5 As shown, when dryness occurs in evaporator 15, evaporator temperature sensor 64 detects the temperature of the refrigerant with superheat. Therefore, the temperature difference obtained by subtracting the evaporator outlet saturation temperature Tsat from the evaporator temperature Tefin exceeds the threshold α1.

[0072] The greater the flow rate of refrigerant into evaporator 15, the larger the threshold value α1 will be. For example... Figure 6 As shown, this is because when the refrigerant flow rate is large, the pressure loss increases, thus creating a pressure difference between the inlet and outlet sides of the evaporator 15, which necessitates suppressing misjudgments caused by the pressure difference.

[0073] If, in step S110, it is determined that the temperature difference obtained by subtracting the evaporator outlet saturation temperature Tsat from the evaporator temperature Tefin does not exceed the threshold α1, proceed to step S120. If, in step S110, it is determined that the temperature difference obtained by subtracting the evaporator outlet saturation temperature Tsat from the evaporator temperature Tefin exceeds the threshold α1, proceed to step S130.

[0074] In step S120, since it is assumed that no drying has occurred in the evaporator 15, the throttling opening EV of the expansion valve 14 is determined to be the normal opening EVN determined in step S100, and then the process proceeds to step S140.

[0075] In step S130, since drying is assumed to have occurred in the evaporator 15, the throttling opening EV of the expansion valve 14 is determined to be an opening EVD (hereinafter referred to as the drying opening) that is greater than the normal opening EVN determined in step S100, and then the process proceeds to step S140. For example, the drying opening EVD is the opening (100%) when the expansion valve 14 is fully open. The drying opening EVD can also be an opening that is a predetermined amount larger than the normal opening EVN.

[0076] In step S140, a control signal or control voltage is output to the expansion valve 14 to obtain the throttling opening EV of the expansion valve 14 determined in steps S120 and S130, and then the process returns to step S100.

[0077] Therefore, in the refrigeration cycle device 10, the state of the refrigerant circulating in the cycle changes as follows: the high-pressure refrigerant discharged from the compressor 11 flows into the condenser 12 and releases heat. As a result, the refrigerant is cooled and condensed in the condenser 12.

[0078] The refrigerant flowing from the condenser 12 undergoes gas-liquid separation in the receiver 13. The liquid refrigerant after separation in the receiver 13 flows into the expansion valve 14, where it is depressurized and expands until it becomes a low-pressure refrigerant. The low-pressure refrigerant after being depressurized in the expansion valve 14 flows into the evaporator 15, where it absorbs heat from the air blown into the vehicle interior and evaporates. As a result, the air blown into the vehicle interior is cooled.

[0079] Then, the refrigerant flowing out of the evaporator 15 flows to the suction side of the compressor 11 and is compressed again in the compressor 11.

[0080] In this way, the refrigeration cycle device 10 can cause the low-pressure refrigerant to absorb heat from the air in the evaporator 15, and then blow the cooled air into the vehicle interior. Thus, the vehicle interior can be cooled.

[0081] In the event of dryness occurring in the evaporator 15, in step S130, the throttling opening EV of the expansion valve 14 is set to a greater than the normal opening EVN, thereby increasing the flow rate of refrigerant into the evaporator 15. This allows the dryness to be eliminated quickly.

[0082] In this embodiment, the detection values ​​of the evaporator temperature sensor 64 and the suction refrigerant pressure sensor 66 are fed back for control, so they are not affected by the tolerance of the expansion valve 14 itself and can be used appropriately up to a low opening degree. Moreover, the superheat obtained at the outlet of the evaporator section 15 is easy to control, and no gas-liquid separation mechanism (so-called liquid receiver) is required between the outlet of the evaporator section 15 and the suction port of the compressor 11, so the suction pressure loss can be reduced, thereby improving performance and efficiency, and reducing manufacturing costs.

[0083] Whether drying has occurred in evaporator 15 is determined by the temperature difference obtained from the evaporator temperature Tefin minus the evaporator outlet saturation temperature Tsat. Therefore, as Figure 7 As shown, even when the temperature of the air flowing into the evaporator 15 is low, it is possible to properly determine whether drying has occurred in the evaporator 15.

[0084] When the temperature of the air flowing into the evaporator 15 is low, and even reducing the opening of the expansion valve 14 cannot achieve sufficient superheat, the expansion valve 14 will operate as follows: Figure 8 The opening degree is repeatedly increased or decreased as shown. In other words, the opening degree of expansion valve 14 swings. Therefore, even if the temperature of the air flowing into evaporator 15 is low, the superheat can be properly controlled by feedback.

[0085] In this embodiment, during normal control of the expansion valve 14, the control device 60 controls the opening of the expansion valve 14 to a normal opening, which is an opening that brings the superheat (SHE) of the refrigerant flowing from the evaporator 15 close to the target superheat (SHEO). The control device 60 determines whether the refrigerant in the evaporator 15 is dry based on the refrigerant temperature (Tefin) detected by the evaporator temperature sensor 64 and the refrigerant pressure (Psuc) detected by the suction refrigerant pressure sensor 66. If the control device 60 determines that the refrigerant in the evaporator 15 is dry, it sets the opening of the expansion valve 14 to a degree greater than the normal opening.

[0086] Therefore, it is possible to properly determine whether the refrigerant in the evaporator 15 is dry. Furthermore, if it is determined that the refrigerant in the evaporator 15 is dry, the flow rate of the refrigerant flowing into the evaporator 15 can be increased, thereby suppressing the drying of the refrigerant in the evaporator 15.

[0087] In this embodiment, a refrigerant suction pressure sensor 66 is provided. This sensor is a first detection unit that detects the state of the refrigerant at a location downstream of the evaporator 15 outlet and upstream of the compressor 11 suction inlet. An evaporator temperature sensor 64 is also provided. This sensor is a second detection unit that detects the state of the refrigerant at a location downstream of the evaporator 15 inlet and upstream of the evaporator 15 outlet. Therefore, it is possible to appropriately determine whether the refrigerant in the evaporator 15 is dry.

[0088] In this embodiment, the control device 60 calculates the refrigerant saturation temperature Tsat based on the refrigerant pressure Psuc detected by the refrigerant pressure sensor 66. If the difference between the refrigerant temperature Tefin detected by the evaporator temperature sensor 64 and the saturation temperature Tsat exceeds the threshold α1, it is determined that the refrigerant in the evaporator 15 is dry.

[0089] Therefore, even when the intake air temperature of the evaporator 15 is low, it is possible to properly determine whether the refrigerant in the evaporator 15 is dry.

[0090] In this embodiment, the greater the flow rate of refrigerant into the evaporator 15, the larger the threshold α1 is set by the control device 60. Therefore, the dryness determination can be more appropriately made by taking into account the pressure loss of the refrigerant in the evaporator 15.

[0091] In this embodiment, the expansion valve control described above is applied to the refrigeration cycle device 10, which has a receiver 13 on the downstream side of the condenser 12 and the upstream side of the expansion valve 14. Therefore, it is easy to use as there is a tendency to close the expansion valve 14. As a result, the phenomenon of liquid refrigerant being drawn into the compressor 11 (i.e., liquid backflow) can be suppressed.

[0092] In this embodiment, when the control device 60 determines that the refrigerant in the evaporator 15 is dry, it controls the expansion valve 14 in a manner that sets the opening of the expansion valve 14 to a degree greater than the normal opening and then returns it to the normal opening. Therefore, after the dryness is eliminated, the expansion valve 14 can be normally controlled, and the refrigeration cycle device 10 can be appropriately controlled.

[0093] In this embodiment, the control device 60 determines the superheat SHE of the refrigerant at the outlet side of the evaporator 15 to be close to the target superheat SHE based on the deviation between the target superheat SHE and the superheat SHE of the refrigerant at the outlet side of the evaporator 15. Therefore, the superheat SHE can be appropriately controlled during normal control.

[0094] (Second Implementation)

[0095] In the first embodiment described above, in the control process of determining the throttling opening EV of the expansion valve 14, if the temperature difference obtained by subtracting the evaporator outlet saturation temperature Tsat from the evaporator temperature Tefin exceeds the threshold α1, the throttling opening EV of the expansion valve 14 is determined as the drying opening EVD.

[0096] In this embodiment, such as Figure 9 As shown, in the control process of determining the throttling opening EV of the expansion valve 14, if the temperature difference obtained by subtracting the evaporator outlet saturation temperature Tsat from the evaporator temperature Tefin exceeds the threshold α1 and the refrigerant flow rate Gr is lower than the threshold β1, the throttling opening EV of the expansion valve 14 is determined to be the drying opening EVD.

[0097] In this embodiment, the throttling opening EV of the expansion valve 14 is determined by... Figure 9 The control process shown in the flowchart determines the value. First, in step S200, similar to step S100 of the first embodiment described above, the normal opening degree EVN of the expansion valve 14 is determined by feedback control, based on the deviation between the target superheat SHEO of the refrigerant at the outlet side of the evaporator 15 and the superheat SHE of the refrigerant at the outlet side of the evaporator 15, in a manner that the superheat SHE is close to the target superheat SHEO. For example, the target superheat SHEO is a predetermined constant (5°C in this embodiment).

[0098] In the next step S210, it is determined whether the temperature difference obtained by subtracting the evaporator outlet saturation temperature Tsat from the evaporator temperature Tefin exceeds a threshold α1 and whether the refrigerant flow rate Gr is below a threshold β1. The refrigerant flow rate Gr is calculated based on the suction refrigerant pressure Psuc detected by the suction refrigerant pressure sensor 66 and the rotational speed of the compressor 11. The refrigerant flow rate Gr can also be detected by a refrigerant flow sensor. The threshold β1 is pre-stored in the control device 60.

[0099] That is, in step S210, it is determined whether it is in the state of Figure 10 The area marked with grid lines (hereinafter referred to as the drying opening area). The drying opening area is the area where drying occurs (in... Figure 10 The area above the solid line (in the middle).

[0100] In step S210, if the temperature difference obtained by subtracting the evaporator outlet saturation temperature Tsat from the evaporator temperature Tefin does not exceed the threshold α1 or the refrigerant flow rate is not lower than the threshold β1 (i.e., it is determined that it is not in the condition of...), then it is determined that it is not in the condition of... Figure 10 If the temperature difference between the evaporator temperature Tefin and the evaporator outlet saturation temperature Tsat exceeds the threshold α1 and the refrigerant flow rate Gr is below the threshold β1 (i.e., it is determined to be in the dry opening range), then proceed to step S220. Figure 10 (Regarding the situation of the drying opening area), proceed to step S230.

[0101] In step S220, similar to step S120 of the first embodiment described above, the throttling opening EV of the expansion valve 14 is determined to be the normal opening EVN determined in step S200, and then the process proceeds to step S240. This is because, when the temperature difference does not exceed the threshold α1, the amount of heat exchange in the evaporator 15 is already low, so even if dryness occurs in the evaporator 15, the performance degradation caused by dryness can be considered minimal. When the refrigerant flow rate is below the threshold β1, even if dryness occurs in the evaporator 15, even if the refrigerant flow rate decreases, the performance degradation will not be a significant problem.

[0102] In step S230, it is assumed that drying has occurred in the evaporator 15. Therefore, similar to step S130 of the first embodiment described above, the throttling opening EV of the expansion valve 14 is determined to be a drying opening EVD that is greater than the normal opening EVN determined in step S200, and then the process proceeds to step S240. For example, the drying opening EVD is the opening degree when the expansion valve 14 is fully open (100%). The drying opening EVD can also be an opening degree that is a predetermined amount larger than the normal opening EVN.

[0103] In step S240, similar to step S240 of the first embodiment described above, a control signal or control voltage is output to the expansion valve 14 to obtain the throttling opening EV of the expansion valve 14 determined in steps S220 and S230, and then the process returns to step S200.

[0104] Therefore, similar to the first embodiment described above, when dryness occurs in the evaporator 15, the throttling opening EV of the expansion valve 14 is set to a greater than the normal opening EVN in step S230, thereby increasing the flow rate of refrigerant into the evaporator 15. This allows for rapid elimination of dryness.

[0105] In this embodiment, the region where the throttling opening EV of the expansion valve 14 is determined as the drying opening EVD is limited to the low flow rate region of the refrigerant, thus simplifying control and reducing design time.

[0106] The present invention is not limited to the embodiments described above, but can be modified in various ways as follows without departing from the spirit of the present invention.

[0107] In the refrigeration cycle device 10 of the above embodiment, a Freon-based refrigerant is used as the refrigerant, but the type of refrigerant is not limited to this, and natural refrigerants such as carbon dioxide and hydrocarbon refrigerants may also be used.

[0108] In addition, the refrigeration cycle device 10 of the above embodiment constitutes a subcritical refrigeration cycle in which the refrigerant pressure on the high-pressure side does not exceed the critical pressure of the refrigerant, but it can also be configured as a supercritical refrigeration cycle in which the refrigerant pressure on the high-pressure side exceeds the critical pressure of the refrigerant.

[0109] The evaporator 15 in the above embodiment allows the refrigerant to exchange heat with air (in other words, a gas), but it is not limited to this; the refrigerant can also exchange heat with cooling water (in other words, a liquid). The evaporator 15 can also be made to contact the object to be cooled, such as a battery, in a heat-transfer manner, and the object to be cooled is cooled by the refrigerant flowing through the evaporator 15.

[0110] The refrigeration cycle device 10 described above is applicable to vehicle air conditioning devices, but its applicability is not limited to this. It can also be applied to battery cooling devices, placement-type air conditioning devices, refrigeration devices, etc.

[0111] This invention has been described based on embodiments, but it should be understood that the invention is not limited to these embodiments or structures. The invention also includes various modifications and variations within the same range. Furthermore, various combinations, arrangements, and other combinations or arrangements that include only one element, or more than or less thereof, are also included within the scope and spirit of this invention.

Claims

1. A refrigeration cycle device, characterized in that, have: A compressor that draws in refrigerant and compresses it before discharging it. A heat-releasing section that causes the refrigerant to release heat; The pressure reducing section reduces the pressure of the refrigerant and can adjust the flow path opening to adjust the flow rate of the refrigerant; An evaporation section that allows the refrigerant, after being depressurized in the depressurization section, to absorb heat from the air; A refrigerant status detection unit detects the status of the refrigerant located downstream of the refrigerant inlet of the pressure reducing unit and upstream of the compressor suction inlet. as well as The control unit controls the opening of the pressure-reducing section to a normal opening, which is an opening that brings the superheat of the refrigerant flowing out of the evaporator close to a target superheat. Based on the refrigerant state detected by the refrigerant state detection unit, the control unit determines whether the refrigerant in the evaporator is dry. If it determines that the refrigerant in the evaporator is dry, the control unit sets the opening of the pressure-reducing section to be greater than the normal opening. The refrigerant state detection unit has: A first detection unit detects the state of the refrigerant located downstream of the outlet of the evaporator and upstream of the inlet of the compressor. as well as The second detection unit detects the state of the refrigerant located downstream of the inlet of the evaporator and upstream of the outlet of the evaporator. The first detection unit detects the pressure of the refrigerant. The second detection unit detects the temperature of the refrigerant. The control unit calculates the saturation temperature of the refrigerant based on the pressure of the refrigerant detected by the first detection unit. If the difference between the temperature of the refrigerant and the saturation temperature detected by the second detection unit exceeds a threshold and the flow rate of the refrigerant flowing into the evaporation unit is lower than a flow rate threshold, it is determined that the refrigerant is dry in the evaporation unit. The refrigerant state detection unit detects the state of the refrigerant located downstream of the refrigerant inlet of the evaporator and upstream of the compressor suction inlet. The higher the flow rate of the refrigerant flowing into the evaporator, the higher the threshold value will be set by the control unit. A liquid storage section is provided on the downstream side of the heat release section and the upstream side of the pressure reduction section. The liquid storage section performs gas-liquid separation of the refrigerant and stores the remaining refrigerant.

2. The refrigeration cycle device according to claim 1, characterized in that, When the control unit determines that the refrigerant is dry in the evaporation section, it controls the pressure reducing section in such a way that it sets the opening of the pressure reducing section to a degree greater than the normal opening and then returns it to the normal opening.

3. The refrigeration cycle device according to claim 1, characterized in that, The control unit determines, based on the deviation between the target superheat and the superheat of the refrigerant flowing out of the evaporation unit, that the superheat of the refrigerant flowing out of the evaporation unit should be close to the target superheat.

Images