JP2009192090A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle device capable of protecting a compressor by estimating excess and deficiency of an amount of refrigerant enclosed in a cycle. <P>SOLUTION: A refrigerant state estimating means decides a state of the refrigerant discharged from a compressor 11 on the basis of a discharged refrigerant temperature Td and a discharged refrigerant pressure Pd of the compressor 11, and from the state, enthalpy of the refrigerant in lowering a pressure to a refrigerant evaporation pressure calculated from a fin temperature Te of an evaporator 14 is determined on an isentropic line. A state of the refrigerant at a gas-liquid separating means outlet side is estimated from the enthalpy, so that it is determined that the amount of enclosed refrigerant is excess when the state of the refrigerant at the gas-liquid separating means outlet side is a gas-liquid two-phase state of less than a reference dryness, and it is determined that the amount of enclosed refrigerant is deficient when the state of the refrigerant at the gas-liquid separating means outlet side is a gas-phase state of more than a reference overheat degree KSH. When the excess or deficiency of the amount of enclosed refrigerant is estimated, an operation of the compressor 11 is stopped. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus including gas-liquid separation means for separating the gas-liquid of refrigerant flowing out of an evaporator.

  Conventionally, Patent Document 1 discloses a refrigeration cycle apparatus configured to be able to estimate the excess or deficiency of the amount of refrigerant enclosed in a cycle. In the refrigeration cycle apparatus of Patent Document 1, the high pressure side refrigerant pressure of the cycle is detected by a pressure sensor, and the excess or shortage of the refrigerant filling amount is estimated using the detected high pressure side refrigerant pressure Pd. And when it determines with the refrigerant | coolant enclosure amount being excessive or insufficient, the operation | movement of a compressor is stopped and the compressor is protected.

  Specifically, when the high-pressure side refrigerant pressure Pd is equal to or higher than the first set pressure Pa, it is estimated that the refrigerant charging amount is excessive, and after a predetermined time has elapsed from the start of the compressor, the second set pressure Pb or lower. If it is, it is presumed that the refrigerant filling amount is insufficient, and further, if it is equal to or lower than the third set pressure Pc before a predetermined time has elapsed since the start of the compressor, the refrigerant filling amount is insufficient. It is estimated.

  At this time, by setting the first to third set pressures such that Pa> Pb> Pc, it is erroneously determined that the refrigerant filling amount is insufficient before a predetermined time has elapsed since the start of the compressor. Is prevented.

As a refrigeration cycle apparatus including a variable capacity compressor, one disclosed in Patent Document 2 or Patent Document 3 is known.
Japanese Patent No. 3404990 JP 2001-173556 A JP 2000-81157 A

  By the way, in the refrigeration cycle apparatus provided with an accumulator as gas-liquid separation means for separating the gas-liquid of the refrigerant flowing out from the evaporator and causing the separated gas-phase refrigerant to flow out to the suction side of the compressor, Therefore, it is necessary to accurately estimate the excess or deficiency. The reason is that in this type of refrigeration cycle apparatus, the cycle is configured assuming that the refrigerant flowing out from the accumulator to the compressor suction side is substantially in a saturated gas phase.

  For example, if the refrigerant charging amount is insufficient, the refrigerant flowing out from the accumulator to the compressor suction side will be in a gas phase state having a superheat degree, the refrigerant flow rate circulating in the cycle will be reduced, and the refrigeration cycle apparatus will Sufficient refrigeration capacity cannot be demonstrated. Furthermore, the refrigeration oil mixed in the refrigerant to lubricate the compressor cannot be returned to the compressor, which causes insufficient compressor lubrication.

  In addition, if the refrigerant filling amount is excessive, the refrigerant flowing out from the accumulator to the compressor suction side becomes a liquid phase state or a gas-liquid two-layer state, which causes a so-called liquid compression problem, and the durability of the compressor. Adversely affects lifespan.

  Further, for example, in a refrigeration cycle apparatus applied to a vehicle air conditioner that uses carbon dioxide having a low critical temperature as a refrigerant, the engine cooling equipment stops operating simultaneously with the stop of the vehicle running engine, and the engine room Due to the so-called dead soak in which the internal temperature rises rapidly, the temperature of the refrigerant sealed in the cycle rises after the cycle is stopped.

  When such a temperature rise of the refrigerant occurs, the refrigerant pressure in the cycle is reduced after the cycle is stopped even if the refrigerant filling amount is slightly excessive so that the above-described liquid compression problem does not occur. May rise abnormally. And such an abnormal rise in refrigerant pressure causes damage to the cycle component equipment.

  However, as in the refrigeration cycle apparatus of Patent Document 1, when the excess or deficiency of the refrigerant filling amount is estimated using only the high-pressure side refrigerant pressure, the refrigeration cycle apparatus is installed as described in Paragraph 0005 of Patent Document 1. Sufficient estimation accuracy cannot be obtained because the range of the high-pressure side refrigerant pressure in which the compressor can be operated changes due to the temperature change of the environment.

  An object of this invention is to provide the refrigerating-cycle apparatus which can estimate accurately the excess and deficiency of the refrigerant | coolant enclosure amount enclosed in the cycle in view of the said point.

  A second object of the present invention is to provide a refrigeration cycle apparatus capable of accurately estimating the excess or deficiency of the amount of refrigerant enclosed in the cycle and protecting the compressor.

  In addition, a third object of the present invention is to provide a refrigeration cycle apparatus that can prevent damage to cycle constituent devices even when the amount of refrigerant enclosed in the cycle is excessive.

  The present invention has been devised in order to achieve the above object. In the invention according to claim 1, the compressor (11) compresses and discharges the refrigerant, and the compressor (11) discharges the refrigerant. A radiator (12) for radiating the refrigerant, a decompression means (13) for decompressing and expanding the refrigerant radiated by the radiator (12), and an evaporator for evaporating the refrigerant decompressed and expanded by the decompression means (13) (14), gas-liquid separation means (15) for separating the gas-liquid refrigerant flowing out of the evaporator (14), and discharge temperature detection means (11) for detecting a physical quantity having a correlation with the compressor (11) discharge refrigerant temperature. 26), a discharge pressure detection means (25) for detecting a physical quantity correlated with the compressor (11) discharge refrigerant pressure, and an evaporation temperature detection means for detecting a physical quantity correlated with the refrigerant evaporation temperature in the evaporator (14). (24) and at least the discharge temperature detection The detected discharge temperature (Td) detected by the means (26), the detected discharge pressure (Pd) detected by the discharge pressure detection means (25), and the detection detected by the evaporation temperature detection means (24) The refrigeration cycle apparatus includes a refrigerant state estimating means (S71) for estimating a refrigerant state on the outlet side of the gas-liquid separation means (15) using the evaporation temperature (Te).

  According to this, the refrigerant state estimating means (S71) uses at least the detected discharge temperature (Td), the detected discharge pressure (Pd), and the detected evaporation temperature (Te), and the gas-liquid separation means (15) outlet side Therefore, it is possible to accurately estimate the excess or deficiency of the amount of refrigerant enclosed in the cycle, when estimating the excess or deficiency of the amount of refrigerant filled using only the high-pressure side refrigerant pressure.

  That is, as will be described in detail in an embodiment described later, if the detected discharge temperature (Td), the detected discharge pressure (Pd), and the detected evaporation temperature (Te) are known, the gas-liquid separation means is obtained from the isentropic line of the refrigerant. The enthalpy of the refrigerant on the outlet side of the gas-liquid separating means (15) flowing out from (15) to the compressor (11) suction side can be obtained. Furthermore, the state of the refrigerant on the outlet side of the gas-liquid separation means (15) can be accurately estimated from this enthalpy.

  Then, if the state of the refrigerant on the outlet side of the gas-liquid separation means (15) accurately estimated is a gas-liquid two-phase state having a dryness equal to or lower than a predetermined dryness, it is estimated that the refrigerant filling amount is excessive. In addition, if the gas phase state has a superheat degree equal to or higher than a predetermined superheat degree, it is possible to accurately estimate the excess or deficiency of the refrigerant charge amount enclosed in the cycle by estimating that the refrigerant charge amount is insufficient.

  According to a second aspect of the present invention, in the refrigeration cycle apparatus according to the first aspect, the discharge capacity changing means (11a) for changing the refrigerant discharge capacity of the compressor (11) and the discharge capacity changing means (11a) The discharge capacity control means (20a) for controlling the operation of the discharge capacity control means (20a) is determined in advance by the refrigerant state estimation means (S71). It is estimated that it is at least one of a gas-liquid two-phase state having a dryness equal to or lower than a reference dryness (KX) and a gas phase state having a superheatability equal to or higher than a predetermined reference superheat (KSH). The operation of the discharge capacity changing means (11a) is controlled so that the refrigerant discharge capacity of the compressor (11) is reduced.

  According to this, the state of the refrigerant on the outlet side of the gas-liquid separation means (15) accurately estimated by the refrigerant state estimation means (S71) has a dryness equal to or lower than a predetermined reference dryness (KX). In the case of at least one of a two-phase state and a gas phase state having a superheat degree equal to or higher than a predetermined reference superheat degree (KSH), the discharge capacity control means (20a) is connected to the compressor (11). Since the refrigerant discharge capacity is reduced, it is possible to protect the compressor (11) by avoiding problems that occur when the compressor (11) is operated when the refrigerant filling amount is excessive or insufficient.

  Note that “reducing the refrigerant discharge capacity of the compressor (11)” in this claim not only means reducing the pressure and flow rate of the refrigerant discharged from the compressor (11), but also compressing. It also includes stopping the operation of the machine (11).

  According to a third aspect of the present invention, in the refrigeration cycle apparatus according to the first or second aspect, the refrigerant state estimating means (S71) sets the refrigerant state at the outlet side of the gas-liquid separating means (15) to a predetermined reference dryness. (KX) It is characterized by comprising warning means (34) for warning the user when it is estimated that the gas-liquid two-phase state having the following dryness.

  According to this, the state of the refrigerant on the gas-liquid separation means (15) outlet side accurately estimated by the refrigerant state estimation means (S71) is a gas-liquid two-phase state having a dryness equal to or lower than a predetermined dryness. In some cases, the warning means (34) issues a warning to the user, so that even if the amount of refrigerant sealed in the cycle is slightly excessive, the environment in which the refrigeration cycle apparatus is installed after the cycle is stopped. It is possible to prevent the cycle component equipment from being damaged due to the temperature rise.

  According to a fourth aspect of the present invention, in the refrigeration cycle apparatus according to any one of the first to third aspects, the refrigerant state estimating means (S71) further determines the compression efficiency (ηc) of the compressor (11). And the refrigerant state on the outlet side of the gas-liquid separation means (15) is estimated. Thereby, the refrigerant | coolant state by the side of a gas-liquid separation means (15) can be estimated still more accurately.

  Note that the “compression efficiency (ηc)” in the present claim is the increase amount ΔH1 of the refrigerant enthalpy when the refrigerant is isentropically compressed by the compressor (11). This is a value obtained by dividing the refrigerant enthalpy increase ΔH2 when the refrigerant is actually boosted by the compressor (11).

  According to a fifth aspect of the present invention, in the refrigeration cycle apparatus according to the fourth aspect of the present invention, the refrigeration cycle apparatus further comprises a rotational speed detecting means (27) for detecting a physical quantity having a correlation with the rotational speed of the compressor (11), so ) Is a value determined based on the detected rotational speed (Ne) detected by the rotational speed detecting means (27).

  Here, when the rotation speed of the compressor (11) increases, the temperature of the refrigerant rises due to the frictional heat and the actual enthalpy increase ΔH2 increases, so the compression efficiency (ηc) also decreases. Therefore, by using the compression efficiency (ηc) determined based on the detected rotation speed (Ne), the refrigerant state on the gas-liquid separation means (15) outlet side can be estimated with higher accuracy.

  According to a sixth aspect of the present invention, in the refrigeration cycle apparatus according to the fourth or fifth aspect, the compression efficiency (ηc) is determined by the detected discharge pressure (Pd) and the suction refrigerant pressure (Ps) of the compressor (11). The value is determined based on the differential pressure (ΔP).

  Here, if the differential pressure (ΔP) between the detected discharge pressure (Pd) and the suction refrigerant pressure (Ps) increases, friction heat is likely to be generated in the compressor (11), and the temperature of the refrigerant increases due to the friction heat. As the actual enthalpy increase ΔH2 increases, the compression efficiency (ηc) also decreases. Therefore, by using the compression efficiency (ηc) determined based on the differential pressure (ΔP), the refrigerant state on the outlet side of the gas-liquid separation means (15) can be estimated with higher accuracy.

  In the invention of claim 7, further comprising an internal heat exchanger (16) for exchanging heat between the refrigerant flowing out of the radiator (12) and the refrigerant sucked into the compressor (11), The estimating means (S71) is further characterized in that the refrigerant state on the outlet side of the gas-liquid separating means (15) is estimated using the heat exchange amount (Hex) in the internal heat exchanger (16).

  According to this, even in the refrigeration cycle apparatus provided with the internal heat exchanger (16), the refrigerant state estimating means (S71) is in the internal heat exchanger (16) of the refrigerant sucked into the compressor (11). Since the estimation is performed using the enthalpy increase, the refrigerant state on the outlet side of the gas-liquid separation means (15) can be estimated with high accuracy.

  Further, as in the invention described in claim 8, the heat exchange amount (Hex) is the refrigerant discharge flow rate of the compressor (11), the detected evaporation temperature (Te), and the radiator of the refrigerant flowing out of the radiator (12). If it is determined based on the outflow refrigerant temperature, the heat exchange amount (Hex) can be easily obtained.

  Further, as in the invention described in claim 9, the compressor (11) may be configured to increase the pressure of the refrigerant until it reaches a critical pressure or more, or as in the invention described in claim 10. The refrigerant may be carbon dioxide. In particular, since the critical temperature of carbon dioxide is about 31 ° C., the pressure easily rises due to the temperature rise in the environment where the refrigeration cycle apparatus is installed after the cycle is stopped. Therefore, it is extremely effective to accurately estimate the excess or deficiency of the refrigerant filling amount.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
1st Embodiment of this invention is described with FIGS. In this embodiment, the refrigeration cycle apparatus 10 of the present invention is applied to a vehicle air conditioner. FIG. 1 is an overall configuration diagram of a refrigeration cycle apparatus 10 according to the present embodiment.

  The refrigeration cycle apparatus 10 employs carbon dioxide as a refrigerant, and constitutes a supercritical refrigeration cycle in which the discharge refrigerant pressure of the compressor 11 is equal to or higher than the critical pressure of the refrigerant (supercritical state). Furthermore, this refrigerant is mixed with refrigerating machine oil for lubricating the compressor 11, and this refrigerating machine oil circulates in the cycle together with the refrigerant.

  The compressor 11 sucks, compresses and discharges the refrigerant in the refrigeration cycle apparatus 10, and is driven to rotate by a driving force transmitted from a vehicle travel engine (not shown) via a pulley and a belt. .

  The compressor 11 is a well-known swash plate type variable displacement compressor configured such that the discharge capacity can be continuously changed by a control signal output from an air conditioning control device 20 described later. The discharge capacity is the geometric volume of the working space where the refrigerant is sucked and compressed, that is, the cylinder volume between the top dead center and the bottom dead center of the piston stroke.

  Specifically, the compressor 11 includes a swash plate chamber (not shown) that introduces suction refrigerant and discharge refrigerant, an electromagnetic capacity control valve 11a that adjusts the ratio of suction refrigerant and discharge refrigerant introduced into the swash plate chamber, It has a swash plate (not shown) that displaces the tilt angle in accordance with the pressure in the swash plate chamber. The piston stroke (discharge capacity) is changed according to the inclination angle of the swash plate.

  The electromagnetic capacity control valve 11a includes a pressure responsive mechanism that generates a force due to a differential pressure between the suction refrigerant pressure and the discharge refrigerant pressure of the compressor 11, and an electromagnetic mechanism that generates an electromagnetic force opposite to the force due to the differential pressure. It is built in and adjusts the valve opening (ratio of suction refrigerant and discharge refrigerant) by the balance between the force due to the differential pressure and the electromagnetic force to change the pressure in the swash plate chamber.

  Further, the electromagnetic force of the electromagnetic mechanism is determined by the control current Ic output from the air conditioning controller 20, and when the control current Ic is increased, the pressure in the swash plate chamber decreases and the inclination angle of the swash plate increases. Thereby, piston stroke (discharge capacity) increases. Conversely, when the control current Ic is decreased, the pressure in the swash plate chamber increases and the tilt angle of the swash plate decreases. Thereby, piston stroke (discharge capacity) decreases.

  Then, since the discharge flow rate of the compressor 11 increases and decreases according to the increase and decrease of the discharge capacity, the electromagnetic capacity control valve 11a constitutes the discharge capacity changing means in the present embodiment. Note that the relationship between the control current Ic and the discharge flow rate of the compressor 11 in the present embodiment is that the discharge flow rate of the compressor 11 increases as the control current Ic increases as shown in the characteristic diagram of FIG. .

  In general, the output of the control current Ic is normally changed by duty control due to the configuration of the current control circuit. However, the value of the control current Ic is directly and continuously controlled regardless of the duty control. It may be changed to (analog). Thus, by adjusting the control current Ic, the compressor 11 can continuously change the discharge capacity in the range of approximately 0% to 100%.

  JP, 2001-173556, A, etc. can be referred to for a capacity control valve and a variable capacity type compressor configured to have such a circulating refrigerant flow rate control function. Furthermore, in this embodiment, the rotation speed sensor 27 for detecting the engine rotation speed of the vehicle running engine is also provided. Accordingly, the refrigerant flow rate Gr circulating in the cycle can be obtained from the rotational speed of the compressor 11 obtained from the control current Ic and the engine rotational speed.

  Further, since the discharge capacity of the compressor 11 of the present embodiment can be reduced to about 0%, as described above, the clutch 11 has a clutchless configuration in which the compressor 11 is always connected to the vehicle running engine via a pulley and a belt. can do. Of course, power may be transmitted from the vehicle running engine via the electromagnetic clutch.

  A radiator 12 is connected to the refrigerant discharge side of the compressor 11. The radiator 12 is a heat-dissipating heat exchanger that performs heat exchange between the high-temperature and high-pressure refrigerant discharged from the compressor 11 and the outside air (air outside the passenger compartment) blown by the cooling fan 12a to radiate the high-pressure refrigerant. The cooling fan 12a is an electric blower in which the rotation speed (the amount of blown air) is controlled by a control voltage output from an air conditioning control device 20 described later.

  As described above, since the refrigeration cycle apparatus 10 of the present embodiment constitutes a supercritical refrigeration cycle, the refrigerant passing through the radiator 12 dissipates heat in a supercritical state without condensing.

  A pressure control valve 13 is connected to the outlet side of the radiator 12. The pressure control valve 13 is a decompression unit that decompresses and expands the high-pressure refrigerant flowing out of the radiator 12, and the valve opening (throttle opening) is a mechanical mechanism so that the high-pressure side refrigerant pressure becomes the target high pressure. It is configured to be adjusted.

  Specifically, the pressure control valve 13 has a temperature sensing portion 13a provided on the outlet side of the radiator 12, and a pressure corresponding to the temperature of the high-pressure refrigerant on the outlet side of the radiator 12 inside the temperature sensing portion 13a. The valve opening degree of the pressure control valve 13 is adjusted by the balance between the internal pressure of the temperature sensing part 13a and the refrigerant pressure on the radiator 12 outlet side.

  Thereby, the high pressure side refrigerant pressure can be adjusted to a target high pressure determined by the high pressure side refrigerant temperature on the outlet side of the radiator 12. For details of the pressure control valve 13 having such a high-pressure control function and the variable displacement compressor, reference can be made to JP-A-2000-81157.

  An evaporator 14 is connected to the outlet side of the pressure control valve 13. The evaporator 14 performs heat exchange between the low-pressure refrigerant decompressed by the pressure control valve 13 and the blown air blown into the vehicle interior from the blower fan 14a, and evaporates the low-pressure refrigerant to exert a heat absorption effect. It is an exchanger. The blower fan 14 a is an electric blower in which the rotation speed (the amount of blown air) is controlled by a control voltage output from the air conditioning controller 20.

  The evaporator 14 is arranged in a case (not shown) that forms an air passage for the air blown into the vehicle interior in the indoor air conditioning unit of the vehicle air conditioner. A heater core, which is a heating means for reheating the blown air by exchanging heat between the blown air cooled by the evaporator 14 and the engine coolant, is disposed. As a result, the temperature of the air blown into the passenger compartment that is air-conditioned space is adjusted.

  An accumulator 15 is connected to the refrigerant outlet side of the evaporator 14. The accumulator 15 is a gas-liquid separator that separates the refrigerant flowing out of the evaporator 14 into a liquid phase refrigerant and a gas phase refrigerant and stores excess liquid phase refrigerant in the cycle. Further, the accumulator 15 is provided with a gas phase refrigerant outlet through which the gas phase refrigerant flows out, and this gas phase refrigerant outlet is connected to the refrigerant suction side of the compressor 11.

  Further, the gas-phase refrigerant outlet is formed in a U-shaped tube that curves downward, and the refrigerating machine oil accumulated in the accumulator 15 is U-shaped at the bottom of the U-shaped tube. A refrigerating machine oil hole is provided for sucking into the pipe. Therefore, ideally, the refrigerant flowing out from the gas-phase refrigerant outlet of the accumulator 15 to the suction side of the compressor 11 does not become a completely saturated gas-phase state but a gas-liquid two-phase state that is very close to the saturated gas-phase state. It becomes.

  Next, an outline of the electric control unit of the present embodiment will be described. The air conditioning control device 20 includes a known microcomputer including a CPU, a ROM, a RAM, and the like and peripheral circuits thereof. Then, various calculations and processes are performed based on the control program stored in the ROM, and the operations of the above-described various electric actuators 11a, 12a, 14a and the like are controlled.

  The air conditioning control device 20 is integrally configured with control means for controlling various electric actuators. In the present embodiment, in particular, the operation of the electromagnetic capacity control valve 11a in the air conditioning control device 20 is performed. The configuration of hardware and software to be controlled is referred to as a discharge capacity control means 20a.

  An air conditioning sensor group 21 to 27 and an operation panel 30 disposed in the passenger compartment are connected to the input side of the air conditioning control device 20. The air conditioning sensor group 21 to 27 detection signals and the operation panel 30 are provided. The operation signals of the various operation switches 31 to 33 are input.

  Specifically, the air conditioning sensor group includes an outside air temperature sensor 21 that detects the outside air temperature Tam, an inside air temperature sensor 22 that detects the inside air temperature Tr, a solar radiation sensor 23 that detects the amount of solar radiation Tsun that enters the vehicle interior, and an evaporator. 14, an evaporator temperature sensor 24 that detects the fin temperature Te, a high-pressure side pressure sensor 25 that detects the discharge refrigerant pressure Pd discharged from the compressor 11, and a high-pressure side that detects the discharge refrigerant temperature Td discharged from the compressor 11. A temperature sensor 26, a rotation speed sensor 27, and the like are provided.

  In the present embodiment, the high-pressure side pressure sensor 25 constitutes a discharge pressure detecting means having a correlation with the compressor 11 discharge refrigerant pressure, and the high-pressure side temperature sensor 26 has a discharge having a correlation with the compressor 11 discharge refrigerant temperature. The evaporator temperature sensor 24 constitutes a temperature detecting means, and the evaporator temperature sensor 24 constitutes an evaporation temperature detecting means for detecting a physical quantity having a correlation with the refrigerant evaporation temperature in the evaporator 14. Further, the rotation sensor 27 is a rotational speed of the compressor 11. The rotation number detecting means for detecting a physical quantity having a correlation with the above is constituted.

  Further, as described above, the pressure control valve 13 of the present embodiment adjusts the high-pressure side refrigerant pressure so as to approach the target high pressure determined by the high-pressure refrigerant temperature on the radiator 12 outlet side, so the high-pressure side on the radiator 12 outlet side. The outside air temperature sensor 21 that detects the outside air temperature Tam close to the refrigerant temperature can also be used as a discharge pressure detecting means.

  Furthermore, since the heat radiator 12 exchanges heat between the refrigerant and the outside air, the outside air temperature sensor 21 of the present embodiment also functions as an air temperature detecting means for detecting the temperature of the air blown to the radiator 12.

  Specifically, the operation switch of the operation panel 30 includes an air conditioner switch 31 that outputs an operation command signal for the vehicle air conditioner, an auto switch 32 that outputs an automatic control request signal for requesting automatic control of the air conditioning state, and a space to be cooled. A temperature setting switch 33 or the like serving as target temperature setting means for setting a target temperature Tset in the vehicle interior is provided.

  Further, on the display panel of the operation panel, the state of the refrigerant at the outlet side of the accumulator 15 that flows out from the accumulator 15 to the suction side of the compressor 11 (hereinafter referred to as gas-liquid separation means outlet side refrigerant) is a predetermined reference dryness KX. When a gas-liquid two-phase state having the following dryness and a gas phase state having a superheat degree equal to or higher than a predetermined reference superheat degree KSH, a warning light that is a warning means for warning the occupant of this is provided. Is provided.

  The output side of the air conditioning controller 20 is connected to the electromagnetic capacity control valve 11a of the compressor 11, the electric actuators such as the electric motors of the cooling fan 12a and the blower fan 14a, and the input side of the operation panel. Is controlled by an output signal of the air conditioning controller 20.

  Next, the operation of the present embodiment having the above configuration will be described with reference to FIGS. 3 and 4 are flowcharts showing the control processing executed by the air conditioning control device 20. This control process starts when the auto switch 32 is turned on (ON) in a state where a vehicle start switch (ignition switch) (not shown) is turned on.

  First, as shown in FIG. 3, in step S1, flags and timers are initialized, and in the next step S2, the detection signals detected by the air conditioning sensor groups 21 to 27 and the operation of the operation panel 30 are performed. Read the signal.

Next, in step S3, a target blowing temperature TAO of the vehicle cabin blowing air is calculated. The target blowing temperature TAO is calculated by the following formula F1 based on the air conditioning thermal load fluctuation and the set temperature Tset set by the temperature setting switch 33.
TAO = Kset × Tset−Kr × Tr−Kam × Tam−Ksun × Tsun + C (F1)
Kset, Kr, Kam, and Ksun are control gains, and C is a correction constant.

  Next, in step S4, control states of various air conditioning control devices excluding the compressor 11 are determined. That is, among various electric actuators connected to the output side of the air conditioning control device 20, control signals to be output to the electric motor of the blower fan 14a and the like excluding the electromagnetic capacity control valve 11a are determined.

  For example, with respect to the control signal (control voltage) output to the electric motor of the blower fan 14a, the control signal stored in the air-conditioning control device 20 in advance is referred to based on the target blowout temperature TAO, and appropriate according to the TAO. It decides so that it may become the amount of blast.

  More specifically, the control voltage is set to the maximum value in the extremely low temperature range (maximum cooling range) and the extremely high temperature range (maximum heating range) of TAO, and the air flow rate is set to the maximum air volume. As the TAO rises from the extremely low temperature range toward the intermediate temperature range, or as the TAO decreases from the extremely high temperature range toward the intermediate temperature range, the control voltage is decreased to reduce the air flow rate. Further, when the TAO enters a predetermined intermediate temperature range, the control voltage is set to the minimum value, and the air volume is set to the minimum air volume.

  Next, the target refrigerant | coolant evaporation temperature TEO in the evaporator 14 is determined in step S5. Specifically, based on the target blowing temperature TAO, the target refrigerant evaporation temperature TEO is determined with reference to a control map stored in the air conditioning control device 20 in advance. In the present embodiment, it is determined that TEO increases as TAO increases.

  Next, in step S6, the refrigerant discharge capacity of the compressor 11 is determined. Specifically, a deviation En (Te−TEO) between the fin temperature Te of the evaporator 14 detected by the evaporator temperature sensor 24 and the target refrigerant evaporation temperature TEO is calculated, and Te is calculated based on the deviation En. The control current Ic output to the electromagnetic capacity control valve 11a is changed by a feedback control method based on proportional-integral control (PI control) so as to approach TEO.

  Next, in step S7, when the state of the gas-liquid separation means outlet side refrigerant flowing out from the accumulator 15 to the compressor 11 suction side is estimated, and the estimation result determines whether the refrigerant filling amount in the cycle is excessive or insufficient. Is controlled. Details of step S7 will be described with reference to the flowchart of FIG.

  First, in step S71, the discharge refrigerant temperature (detection discharge temperature) Td detected by the high pressure side temperature sensor 26, the discharge refrigerant pressure (detection discharge pressure) Pd detected by the high pressure side pressure sensor 25, and the evaporator Using the fin temperature (detected evaporation temperature) Te detected by the temperature sensor 24, the state of the gas-liquid separation means outlet side refrigerant is estimated. Therefore, in this embodiment, this step S71 constitutes a refrigerant state estimating means.

  Details of the estimation of the state of the gas-liquid separation means outlet side refrigerant in step S71 will be described with reference to the Mollier diagram of FIG. First, the state of the refrigerant discharged from the compressor 11 (point Cout in FIG. 5) is determined by the discharged refrigerant temperature Td and the discharged refrigerant pressure Pd. Further, since the fin temperature Te is a value corresponding to the refrigerant evaporation temperature in the evaporator 14, the refrigerant evaporation pressure Ps in the evaporator 14 is obtained from the fin temperature Te.

  Here, since the refrigerant sucked into the compressor 11 is isentropically compressed by the compressor 11, it is on the isentropic line passing through the above-mentioned point Cout, and the refrigerant pressure becomes the refrigerant evaporation pressure Ps. The enthalpy of the gas-liquid separation means outlet side refrigerant is obtained from the point (point Cin in FIG. 5), and the state of the gas-liquid separation means outlet side refrigerant can be estimated by this enthalpy.

  Note that, in the refrigeration cycle apparatus including the accumulator 15 as in the present embodiment, ideally, the state of the refrigerant on the gas-liquid separation means outlet side is substantially on the saturated gas line unless the refrigerant filling amount is excessive or insufficient. .

  Therefore, for example, when the state of the refrigerant discharged from the compressor 11 is the point Cout1, since the enthalpy of the gas-liquid separation means outlet side refrigerant has not reached the saturated gas line, the refrigerant state is a gas-liquid two-phase state. When the state of the refrigerant discharged from the compressor 11 is the point Cout2, the enthalpy of the gas-liquid separation means outlet side refrigerant exceeds the saturated gas line, so the refrigerant state is overheated. Gas phase state (point Cin2 in FIG. 5).

  Next, as shown in FIG. 4, in step S72, the gas-liquid two-phase in which the state Cin of the gas-liquid separation means outlet-side refrigerant estimated in step S71 has a dryness equal to or lower than a predetermined reference dryness KX. It is determined whether or not it is in a state. When the state Cin of the refrigerant at the outlet side of the gas-liquid separation means is in a gas-liquid two-phase state having a dryness equal to or lower than a predetermined reference dryness KX, the amount of refrigerant enclosed in the cycle is excessive. As a result, the process proceeds to step S74.

  In step S74, the warning lamp 34 is turned on, and further, the process proceeds to step S75, and the electromagnetic capacity control valve is set so that the discharge capacity of the compressor 11 becomes substantially 0%, that is, the operation of the compressor 11 is stopped. The control current Ic output to 11a is changed and the process proceeds to step S8. On the other hand, if it is determined in step S72 that the state Cin of the gas-liquid separation means outlet side refrigerant is not a gas-liquid two-phase state having a dryness equal to or lower than a predetermined reference dryness (KX), the process proceeds to step S73.

  In step S73, it is determined whether or not the state Cin of the gas-liquid separation means outlet side refrigerant is in a gas phase state having a superheat degree equal to or higher than a predetermined reference superheat degree KSH. If the state Cin of the gas-liquid separation means outlet side refrigerant is in a gas phase state having a superheat degree equal to or higher than a predetermined reference superheat degree KSH, it is assumed that the refrigerant filling amount is insufficient and steps S74 → S75. → Proceed in the order of S8.

  On the other hand, if the state Cin of the gas-liquid separation means outlet side refrigerant is not in a gas phase state having a superheat degree equal to or higher than a predetermined reference superheat degree (KSH) in step S73, there is no excess or deficiency of the refrigerant filling amount. As a thing, it progresses to step S8.

  In step S8, a control signal is output from the air conditioning control device 20 to the electric actuator so that the control state determined in steps S4 and S7 is obtained. In the next step S9, the process waits for the control period τ, and when it is determined that the control period τ has elapsed, the process returns to step S2.

  In the present embodiment, when the operation is performed as described above and it is determined that there is no excess or deficiency of the refrigerant filling amount, the refrigerant discharged from the compressor 11 is discharged from the radiator 12 → the pressure control valve 13 → the evaporator 14. By circulating in the order of the accumulator 15 → the compressor 11, the air blown into the passenger compartment can be cooled by the evaporator 14.

  On the other hand, when it is determined that the refrigerant filling amount is excessive or insufficient, the discharge capacity control means 20a substantially stops the operation of the compressor 11. Therefore, when the refrigerant charging amount is excessive or insufficient, the compressor 11 is turned off. The compressor 11 can be protected by avoiding problems such as insufficient lubrication of the compressor 11 and liquid compression that occur when the compressor 11 is used.

  At this time, in the control step S71 constituting the refrigerant state estimating means, the state of the refrigerant at the outlet side of the gas-liquid separating means is estimated using the discharged refrigerant temperature Td, the discharged refrigerant pressure Pd, and the fin temperature Te. In contrast to the case where the excess / deficiency of the refrigerant filling amount is estimated using only the side refrigerant pressure, the excess / deficiency of the refrigerant filling amount enclosed in the cycle can be accurately estimated.

  In the present embodiment, in order to accurately estimate the excess or deficiency of the refrigerant filling amount, specifically, the reference dryness KX = 0.85 and the reference superheat KSH = 10 ° C. Further, according to the study by the present inventors, it has been found that it is preferable to set the standard dryness KX = 0.9 and the standard superheat KSH = 5 ° C.

  Further, when it is estimated that the refrigerant filling amount is excessive or insufficient, the warning lamp is turned on in step S74, so that the user can recognize whether the refrigerant filling amount is excessive or insufficient. As a result, for example, even if the amount of refrigerant enclosed in the cycle is slightly excessive, the cycle components are damaged by dead soak after the cycle is stopped due to measures such as removing the refrigerant. This can be prevented beforehand.

(Second Embodiment)
In the above-described embodiment, the state of the refrigerant on the gas-liquid separation means outlet side is estimated using isentropic lines as shown in FIG. 5 by utilizing the isentropic compression of the refrigerant by the compressor 11. In the present embodiment, an example in which the state of the gas-liquid separation unit outlet-side refrigerant is estimated using the compression efficiency ηc of the compressor 11 will be described.

  Here, the compression efficiency ηc will be described with reference to the Mollier diagram of FIG. The compression efficiency ηc of the present embodiment is the increase in refrigerant enthalpy ΔH1 when the refrigerant is isentropically compressed by the compressor 11, and the increase in refrigerant enthalpy when the refrigerant is actually boosted by the compressor 11. It is defined by the value divided by the minute ΔH2.

  As shown in FIG. 6, the amount of increase enthalpy ΔH1 in ideal isentropic compression (Cin → Cout in FIG. 6) is the compression stroke (Cin → Cout in FIG. 6) in which the refrigerant is boosted in the actual compressor 11. It becomes smaller than the enthalpy increase ΔH2 in '). This is because power loss due to friction or the like occurs in the compression mechanism portion of the compressor 11, and heat generated by the power loss heats the refrigerant.

  Further, the compression efficiency ηc decreases as the number of revolutions of the compressor 11 increases as shown in FIG. 7, and as shown in FIG. 8, the compressor 11 discharge refrigerant pressure Pd and the intake refrigerant pressure Ps. It decreases as the pressure difference ΔP increases. Therefore, in the present embodiment, in the control step S71 constituting the refrigerant state estimating means, the state of the gas-liquid separating means outlet side refrigerant is estimated as follows. The overall configuration of the refrigeration cycle apparatus 10 is the same as that of the first embodiment.

  In step S71 of this embodiment, in addition to the discharge refrigerant temperature Td, the discharge refrigerant pressure Pd, and the fin temperature Te, the gas-liquid separation means is used using the rotation speed Ne detected by the rotation speed sensor 27 that detects the engine rotation speed. The state of the outlet side refrigerant is estimated. As described above, the detected rotational speed Ne of the rotational speed sensor 27 has a correlation with the rotational speed of the compressor 11.

  Further, since the fin temperature Te has a correlation with the refrigerant evaporation pressure Ps, the pressure difference ΔP can be obtained from the discharged refrigerant pressure Pd and the fin temperature Te. Therefore, in the present embodiment, the compression efficiency ηc of the compressor 11 is determined with reference to a control map stored in advance based on the detected rotation speed Ne, the discharge refrigerant pressure Pd, and the fin temperature Te.

  Further, similarly to the first embodiment, the state of the refrigerant discharged from the compressor 11 and the refrigerant evaporation pressure Ps in the evaporator 14 are determined, and based on the isentropic curve corrected by the compression efficiency ηc, the gas-liquid separation means outlet side The enthalpy of the refrigerant is obtained, and the state of the refrigerant on the gas-liquid separation means outlet side is estimated based on this enthalpy.

  More specifically, similarly to the first embodiment, the enthalpy of the refrigerant on the isentropic line of the refrigerant discharged from the compressor 11 at the point where the refrigerant pressure becomes the refrigerant evaporation pressure Ps is set as a temporary enthalpy. Then, a value obtained by subtracting the temporary enthalpy from the enthalpy of the refrigerant discharged from the compressor 11 is set as a temporary enthalpy increase amount.

  Further, a value obtained by dividing the temporary enthalpy increase amount by the compression efficiency ηc is set as an actual enthalpy increase amount of the refrigerant on the gas-liquid separation means outlet side with respect to the refrigerant discharged from the compressor 11. Then, by subtracting the actual enthalpy increase from the enthalpy of the refrigerant discharged from the compressor 11, the enthalpy of the gas-liquid separation means outlet side refrigerant is estimated.

  In this embodiment, the compression efficiency ηc is determined using the detected rotation speed Ne and the differential pressure ΔP between the discharge refrigerant pressure Pd and the suction refrigerant pressure Ps, and the state of the gas-liquid separation means outlet side refrigerant is determined using this compression efficiency ηc. Therefore, the state of the refrigerant flowing out from the accumulator 15 to the suction side of the compressor 11 can be estimated with higher accuracy.

  As a result, it is possible to estimate the excess or deficiency of the amount of refrigerant enclosed in the cycle with higher accuracy and appropriately protect the compressor, and to damage the cycle component equipment. Can be prevented appropriately.

(Third embodiment)
In the refrigeration cycle apparatus 10 of the present embodiment, as shown in FIG. 9, an internal heat exchanger 16 is provided for the first embodiment described above. FIG. 9 is an overall configuration diagram of the refrigeration cycle apparatus 10 of the present embodiment. Moreover, in FIG. 9, the same code | symbol is attached | subjected to the same or equivalent part as 1st Embodiment.

  The internal heat exchanger 16 exchanges heat between the radiator 12 outlet-side refrigerant passing through the high-pressure side refrigerant flow path 16a and the compressor 11 suction-side refrigerant passing through the low-pressure side refrigerant flow path 16b. The refrigerant passing through 16a is cooled. Thereby, the enthalpy difference (refrigeration capacity) between the enthalpy of the inlet side refrigerant and the enthalpy of the outlet side refrigerant in the evaporator 14 can be increased.

  As a specific configuration of the internal heat exchanger 16, a configuration in which the refrigerant pipes forming the high-pressure side refrigerant flow path 16a and the low-pressure side refrigerant flow path 16b are brazed and joined to exchange heat, or the high-pressure side refrigerant flow is set. A double-pipe heat exchanger configuration in which the low-pressure side refrigerant flow path 16b is disposed outside the inner pipe forming the path 16a can be employed.

  By the way, in the cycle including the internal heat exchanger 16 as in this embodiment, the refrigerant flowing out of the evaporator 14 is heated by the refrigerant on the outlet side of the radiator 12 and then sucked into the compressor 11. Therefore, when the state of the compressor suction side refrigerant flowing out from the accumulator 15 to the compressor 11 side is estimated by the same method as in the first embodiment, the low pressure side refrigerant flow path 16b of the internal heat exchanger 16 is moved to the compressor 11 side. The state of the refrigerant flowing out will be estimated.

  Therefore, in step S71 of this embodiment, in addition to the discharge refrigerant temperature Td, the discharge refrigerant pressure Pd, and the fin temperature Te, the outside air temperature Tam, the detected rotation speed Ne, and the refrigerant on the outlet side of the radiator 12 in the internal heat exchanger 16 and the compression are compressed. The state of the compressor suction-side refrigerant is estimated using the heat exchange amount Hex with the compressor 11 suction-side refrigerant.

This heat exchange amount Hex can be determined based on the refrigerant discharge flow rate of the compressor 11, the fin temperature Te, and the outside air temperature Tam. Specifically, the intake refrigerant temperature Ts sucked into the compressor 11 is obtained by the following formula F2.
Ts = f (Te, Tam, Gr, φ) (F2)
Gr is the flow rate of the refrigerant circulating in the cycle, and φ is the heat exchange efficiency of the internal heat exchanger 16.

  Here, the refrigerant flow rate Gr circulating through the cycle, that is, the compressor 11 discharge refrigerant flow rate can be obtained from the rotation speed of the compressor 11 obtained from the control current Ic and the detected rotation speed Ne as described above. Furthermore, the heat exchange efficiency φ is a value determined by the length of each refrigerant flow path 16a, 16b of the internal heat exchanger 16, the heat transfer coefficient, and the like.

  Then, if the suction refrigerant temperature Ts and the fin temperature Te obtained by the above formula F2 are compared, that is, the refrigerant evaporation temperature in the evaporator 14, the temperature rise amount of the gas-liquid separation means outlet side refrigerant in the internal heat exchanger 16, That is, the heat exchange amount Hex can be obtained.

  Further, similarly to the first embodiment, the enthalpy of the refrigerant on the isentropic line of the refrigerant discharged from the compressor 11 at the point where the refrigerant pressure becomes the refrigerant evaporation pressure Ps is set as a temporary enthalpy. Then, by subtracting the enthalpy amount corresponding to the heat exchange amount Hex from the temporary enthalpy, the enthalpy of the gas-liquid separation means outlet side refrigerant can be estimated.

  In the present embodiment, as described above, even in the refrigeration cycle apparatus including the internal heat exchanger 16, the excess or deficiency of the amount of refrigerant enclosed in the cycle is accurately estimated as in the first embodiment. Thus, it is possible to protect the compressor and to prevent the cycle component equipment from being damaged.

  In the configuration of the present embodiment, the state of the gas-liquid separation means outlet side refrigerant may be estimated using the compression efficiency ηc, as in the second embodiment. As a result, it is possible to estimate the excess or deficiency of the amount of refrigerant enclosed in the cycle with higher accuracy and appropriately protect the compressor, and to appropriately damage the cycle component equipment. Can be prevented.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be variously modified as follows.

  (1) In the above-described embodiment, the example in which the swash plate type variable displacement compressor 11 is employed as the compressor and the electromagnetic displacement control valve 11a is employed as the discharge capacity changing means has been described. The means is not limited to this. For example, you may employ | adopt the electric compressor comprised by the fixed capacity type compressor and the electric motor.

  In this case, the refrigerant flow rate Gr circulating in the cycle can be obtained by integrating the number of revolutions of the electric motor to the discharge capacity per revolution of the compressor. Furthermore, since the rotation speed of the electric motor can be detected by the control voltage and control frequency output to the electric motor, the rotation speed sensor 27 may not be provided.

  (2) In the above-described embodiment, the example in which the refrigerant flow rate Gr is calculated using the control current Ic output from the air conditioning control device 20 to the electromagnetic capacity control valve 11a has been described. You may provide the flow sensor to detect. Specifically, a mass flow sensor such as a differential pressure flow sensor or a hot wire flow sensor may be employed as the flow sensor.

  (3) In the above-described embodiment, the example in which the evaporator temperature sensor 24 that detects the fin temperature Te of the evaporator 14 is employed as the evaporation temperature detecting means has been described. For example, the surface temperature of the outlet pipe of the evaporator 14 is detected. A temperature sensor that directly detects the refrigerant temperature in the evaporator 14 or a pressure sensor that detects the refrigerant evaporation pressure in the evaporator 14 can also be employed as the evaporation temperature detecting means.

  (4) In the second embodiment, the example in which the compression efficiency ηc is determined using the detected rotation speed Ne and the differential pressure ΔP between the discharge refrigerant pressure Pd and the suction refrigerant pressure Ps has been described. The compression efficiency ηc determined using any one of the differential pressures ΔP may be used.

  (5) In the above embodiment, as shown in the flowchart of FIG. 3, the state of the gas-liquid separation means outlet side refrigerant is estimated for each control period during the operation of the cycle, and the state of the gas-liquid separation means outlet side refrigerant is estimated. However, the state of the gas-liquid separation means outlet side refrigerant and the determination of the excess or deficiency of the refrigerant filling amount may be performed only immediately after the start of the cycle.

  (6) In the above-described embodiment, a warning lamp is used as the warning means. However, for example, an acoustic device that issues a warning by sound, a vibrating device that generates a warning by vibration, or the like may be used.

  (7) In the above-described embodiment, an example in which the refrigeration cycle apparatus 10 of the present invention is applied to a vehicle air conditioner has been described, but the application of the present invention is not limited to this. For example, the present invention may be applied to a commercial refrigeration apparatus, a household refrigerator, and the like.

  (8) In the above-described embodiment, the radiator 12 is an outdoor heat exchanger that exchanges heat between the refrigerant and the outside air, and the evaporator 14 is an indoor heat exchanger that is applied for cooling the vehicle interior. The present invention is applied to a heat pump cycle in which the evaporator 14 is configured as an outdoor heat exchanger that absorbs heat from a heat source such as outside air, and the radiator 12 is configured as an indoor heat exchanger that heats a heated fluid such as air or water. May be.

It is a whole lineblock diagram of the refrigerating cycle device of a 1st embodiment. It is a characteristic view which shows the relationship between a control current and a compressor discharge refrigerant | coolant flow rate. It is a flowchart which shows control of the refrigerating-cycle apparatus of 1st Embodiment. It is a flowchart which shows the principal part of control of the refrigerating-cycle apparatus of 1st Embodiment. It is a Mollier diagram which shows the state of the refrigerant | coolant of 1st Embodiment. It is a Mollier diagram for demonstrating the compression efficiency of 2nd Embodiment. It is a graph which shows the change of the compression efficiency with respect to compressor rotation speed. It is a graph which shows the change of compression efficiency with respect to the differential pressure of compressor discharge refrigerant pressure and suction refrigerant pressure. It is a whole block diagram of the refrigerating-cycle apparatus of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Compressor 11a Electromagnetic capacity control valve 12 Radiator 13 Pressure control valve 14 Evaporator 15 Accumulator 16 Internal heat exchanger 24 Evaporator temperature sensor 25 High pressure side pressure sensor 26 High pressure side temperature sensor 27 Rotation sensor 34 Warning light S71 Refrigerant state Estimating means

Claims (10)

A compressor (11) for compressing and discharging the refrigerant;
A radiator (12) for radiating the refrigerant discharged from the compressor (11);
Decompression means (13) for decompressing and expanding the refrigerant radiated by the radiator (12);
An evaporator (14) for evaporating the refrigerant decompressed and expanded by the decompression means (13);
Gas-liquid separation means (15) for separating the gas-liquid of the refrigerant flowing out of the evaporator (14);
A discharge temperature detection means (26) for detecting a physical quantity having a correlation with the compressor (11) discharge refrigerant temperature;
A discharge pressure detection means (25) for detecting a physical quantity having a correlation with the compressor (11) discharge refrigerant pressure;
Evaporating temperature detecting means (24) for detecting a physical quantity having a correlation with the refrigerant evaporating temperature in the evaporator (14);
At least the detected discharge temperature (Td) detected by the discharge temperature detecting means (26), the detected discharge pressure (Pd) detected by the discharge pressure detecting means (25), and the evaporation temperature detecting means (24 Refrigeration cycle apparatus comprising refrigerant state estimation means (S71) for estimating the refrigerant state on the outlet side of the gas-liquid separation means (15) using the detected evaporation temperature (Te) detected in (1). . Furthermore, discharge capacity changing means (11a) for changing the refrigerant discharge capacity of the compressor (11),
A discharge capacity control means (20a) for controlling the operation of the discharge capacity changing means (11a),
The discharge capacity control means (20a) is configured so that the refrigerant state on the outlet side of the gas-liquid separation means (15) has a dryness equal to or lower than a predetermined reference dryness (KX) by the refrigerant state estimation means (S71). When it is estimated that the state is at least one of a liquid two-phase state and a gas phase state having a superheat degree equal to or higher than a predetermined reference superheat degree (KSH), the refrigerant discharge of the compressor (11) The refrigeration cycle apparatus according to claim 1, wherein the operation of the discharge capacity changing means (11a) is controlled so as to reduce the capacity.   The refrigerant state estimating means (S71) estimated that the refrigerant state at the outlet side of the gas-liquid separating means (15) is a gas-liquid two-phase state having a dryness equal to or lower than a predetermined reference dryness (KX). The refrigeration cycle apparatus according to claim 1 or 2, further comprising warning means (34) for warning the user of this.   The refrigerant state estimating means (S71) further estimates the refrigerant state on the outlet side of the gas-liquid separating means (15) using the compression efficiency (ηc) of the compressor (11). Item 4. The refrigeration cycle apparatus according to any one of Items 1 to 3. A rotation speed detection means (27) for detecting a physical quantity having a correlation with the rotation speed of the compressor (11);
The refrigeration cycle apparatus according to claim 4, wherein the compression efficiency (ηc) is a value determined on the basis of the detected rotational speed (Ne) detected by the rotational speed detecting means (27). .   The compression efficiency (ηc) is a value determined based on a differential pressure (ΔP) between the detected discharge pressure (Pd) and a suction refrigerant pressure (Ps) of the compressor (11). The refrigeration cycle apparatus according to claim 4 or 5. And an internal heat exchanger (16) for exchanging heat between the refrigerant flowing out of the radiator (12) and the refrigerant sucked into the compressor (11),
The refrigerant state estimating means (S71) further estimates the refrigerant state on the outlet side of the gas-liquid separation means (15) using the heat exchange amount (Hex) in the internal heat exchanger (16). The refrigeration cycle apparatus according to any one of claims 1 to 6.   The heat exchange amount (Hex) is based on the refrigerant discharge flow rate (Gr) of the compressor (11), the detected evaporation temperature (Te), and the radiator outflow refrigerant temperature of the refrigerant flowing out of the radiator (12). The refrigeration cycle apparatus according to claim 7, wherein the refrigeration cycle apparatus has a determined value.   The refrigeration cycle apparatus according to any one of claims 1 to 8, wherein the compressor (11) increases the pressure of the refrigerant until the pressure becomes a critical pressure or more.   The refrigeration cycle apparatus according to any one of claims 1 to 9, wherein the refrigerant is carbon dioxide.

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