JP2006177598A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To resolve a problem in a refrigerating cycle device provided with an injection circuit injecting a gas refrigerant separated by a gas-liquid separator 5 into a compressor 1 wherein performance is deteriorated and reliability of the compressor is deteriorated when a temperature difference between an indoor temperature and an outside air temperature is small since dryness of a refrigerant in the gas-liquid separator 5 becomes small, and a great deal of a liquid refrigerant is injected. <P>SOLUTION: The refrigerating cycle device is provided with an outside air temperature detecting means 21, an indoor air temperature detecting means 22, an opening and closing valve 8 capable of carrying out full closing provided between the compressor 1 and the gas-liquid separator 5 of the injection circuit 9, and a control means for detecting the outside air temperature and the indoor air temperature, and carrying out full closing of the opening and closing valve when the difference between the outside air temperature and the indoor air temperature is a predetermined value or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a refrigeration cycle apparatus.

  A first throttle device capable of changing the throttle amount, such as a compressor, a four-way valve, an outdoor heat exchanger, and an electric expansion valve; a second throttle device capable of changing the throttle amount, such as a gas-liquid separator, an electric expansion valve; The refrigeration cycle is configured by sequentially connecting indoor heat exchangers through the refrigerant piping, and the gaseous refrigerant that has reached the intermediate pressure between the condensation pressure and the evaporation pressure separated by the gas-liquid separator is injected into the intermediate pressure part of the compressor. Patent Document 1 discloses an air conditioner including a refrigeration cycle that is injected by piping.

  In this Patent Document 1, it is determined that liquid injection is performed when the compressor rotational speed is equal to or lower than a set value, when the outside air temperature is equal to or lower than a predetermined temperature, or when the room temperature is equal to or higher than a predetermined value during cooling operation. In addition, it is described that the two-way valve provided in the injection pipe is closed to stop the injection. Also, during the heating operation, it is determined that the liquid injection is performed when the compressor rotation speed is equal to or lower than the predetermined value, the outside air temperature is equal to or higher than the predetermined temperature, or the room temperature is equal to or lower than the predetermined value. It is described that the two-way valve provided is closed to stop the injection.

JP 2002-81769 A

  In the prior art described in Patent Document 1, for example, when the outside air temperature is lower than a predetermined temperature during the cooling operation, the two-way valve is closed to stop the injection regardless of the indoor air temperature. This prevents injection and prevents performance degradation and compressor reliability degradation.

  However, during the cooling operation, even if the outside air temperature is low, if the room air temperature is low to some extent, it is possible to separate the gas refrigerant and sufficiently increase the injection effect. In the conventional technology, when the outside air temperature during cooling operation is low, the condensation of the outdoor heat exchanger proceeds, the subcooling increases, the gas-liquid separator becomes rich, and the amount of gas refrigerant to be injected decreases, so liquid injection tends to occur. So stop the injection. However, when the outside air temperature is low but the room air temperature is also low, liquid refrigerant collects in the outdoor heat exchanger, and thus the pressure (evaporation pressure) of the indoor heat exchanger decreases, so the gas refrigerant in the gas-liquid separator Increases, so gas injection becomes possible.

  As described above, in the prior art, whether or not to perform the injection is determined depending on each of the outside air temperature and the indoor air temperature. Therefore, although the injection is possible, there is a problem in that the performance is deteriorated by stopping the injection. That is, the conventional technique is effective in terms of preventing liquid injection by a simple method, but there is still room for improvement in order to enjoy the effect of gas injection to the maximum extent.

  An object of the present invention is to expand a region where gas injection is performed in a refrigeration cycle apparatus that performs gas injection while preventing a decrease in performance and a decrease in compressor reliability due to a large amount of liquid refrigerant being injected. It is to improve performance.

  The purpose is to sequentially connect a compressor, a four-way valve, an outdoor heat exchanger, a first expansion means, a gas-liquid separator, a second expansion means, and an indoor heat exchanger. In the refrigeration cycle apparatus comprising a connected refrigeration cycle and an injection pipe for guiding the refrigerant separated by the gas-liquid separator to the compressor, the injection pipe between the gas-liquid separator and the compressor A provided on-off valve capable of being fully closed; an outside air temperature detecting means for detecting an outside air temperature; an indoor air temperature detecting means for detecting an indoor air temperature; the outside air temperature detected by the outside air temperature detecting means; This is achieved by providing a refrigeration cycle apparatus including a control unit that fully closes the on-off valve when the difference between the detected air temperature and the indoor air temperature is a predetermined value or less.

  Further, the object is to provide a two-stage compressor that sucks and discharges refrigerant discharged from the low-pressure side compression mechanism into the high-pressure side compression mechanism, an outdoor heat exchanger, and first expansion means that can adjust the opening degree, A refrigeration cycle in which a gas-liquid separator, a second expansion means with adjustable opening degree, and an indoor heat exchanger are connected by piping, and a gas refrigerant separated by the gas-liquid separator is a two-stage compressor In the refrigeration cycle apparatus comprising an injection pipe that leads to an intermediate pressure space provided between the low-pressure side compression mechanism and the high-pressure side compression mechanism, an on-off valve that can be fully closed provided in the injection pipe, Outdoor heat exchanger refrigerant temperature detecting means for detecting the refrigerant temperature of the outdoor heat exchanger, indoor heat exchanger refrigerant temperature detecting means for detecting the refrigerant temperature of the indoor heat exchanger, and the outdoor heat exchange Chamber detected by the refrigerant temperature detection means Control means for fully closing the on-off valve when a difference between the side heat exchanger refrigerant temperature and the indoor side heat exchanger refrigerant temperature detected by the indoor side heat exchanger refrigerant temperature detection means is equal to or less than a predetermined value; This is achieved by providing a refrigeration cycle apparatus provided.

  Further, the object is to provide a two-stage compressor that sucks and discharges refrigerant discharged from the low-pressure side compression mechanism into the high-pressure side compression mechanism, an outdoor heat exchanger, and first expansion means that can adjust the opening degree, A refrigeration cycle in which a gas-liquid separator, a second expansion means with adjustable opening degree, and an indoor heat exchanger are connected by piping, and a gas refrigerant separated by the gas-liquid separator is a two-stage compressor In the refrigeration cycle apparatus comprising an injection pipe that leads to an intermediate pressure space provided between the low-pressure side compression mechanism and the high-pressure side compression mechanism, an on-off valve that can be fully closed provided in the injection pipe, A discharge temperature detection means for detecting a discharge refrigerant temperature of the compressor; a discharge temperature target value setting means for setting a target value of the discharge refrigerant temperature of the compressor; and a temperature detected by the discharge temperature detection means is the discharge temperature target. Setting of value setting means And than the temperature achieved by the refrigeration cycle apparatus and control means for said opening and closing valve is fully closed when a predetermined value or more lower.

  According to the present invention, in a refrigeration cycle apparatus that performs gas injection, by expanding a region where gas injection is performed while preventing a decrease in performance and a decrease in compressor reliability due to a large amount of liquid refrigerant being injected. Performance can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a room air conditioner (air conditioner) will be described as an embodiment to be applied. FIG. 1 is a cycle configuration diagram of a refrigeration cycle apparatus according to an embodiment of the present invention. FIG. 2 is a Mollier diagram showing the difference in the refrigeration cycle due to the difference in indoor and outdoor temperature differences. FIG. 3 is a Mollier diagram showing the difference in the refrigeration cycle due to the difference in indoor air temperature when the outside air temperature is the same. FIG. 4 is a Mollier diagram showing the difference in the refrigeration cycle when the indoor air temperature and the outdoor air temperature are different but the indoor / outdoor temperature difference is relatively close. FIG. 5 is a diagram showing conditions for determining opening / closing of the on-off valve provided in the injection circuit in accordance with the indoor air temperature and the outside air temperature during the cooling operation. FIG. 6 is a diagram showing conditions for determining opening and closing of the on-off valve provided in the injection circuit according to the indoor air temperature and the outside air temperature during the heating operation. FIG. 7 is a block diagram of a control device that controls the on-off valve in accordance with the difference between the indoor air temperature and the outside air temperature. FIG. 8 is a Mollier diagram showing changes in the refrigeration cycle depending on the flow rate of the liquid refrigerant to be injected and changes in the temperature difference between the two refrigerant temperature sensors provided for injection control. FIG. 9 is a diagram showing the relationship between the downstream electric expansion valve opening and the temperature difference between the two refrigerant temperature sensors.

  In FIG. 1, reference numeral 1 denotes a compressor, and a two-stage compressor is applied in this embodiment. 2 is a four-way valve, 3 is an outdoor heat exchanger, 4 is a first electric expansion valve, 5 is a gas-liquid separator, 6 is a second electric expansion valve, 7 is an indoor heat exchanger, and 8 is an on-off valve. , 9 is an injection pipe, and 10 is a refrigerant pipe communicating the first stage outlet and the second stage inlet of the two-stage compressor. 21 is an outside air temperature sensor that detects the temperature of the outside air, 22 is an indoor air temperature sensor that detects the air temperature in the room, and 23 is in the vicinity of the refrigerant pipe 10 that communicates the first stage outlet and the second stage inlet of the compressor. The injection refrigerant temperature sensor provided in the injection pipe 9, 24 is an intermediate temperature sensor provided between the first electric expansion valve 4 and the gas-liquid separator 5, and 25 detects the discharge refrigerant temperature of the compressor 1. Discharge refrigerant temperature sensor, 30 is a control device, 31 is a computing device such as a microcomputer provided in the control device 30, 32 is a storage device provided in the control device 30, and 41 is the first stage of the two-stage compressor The compression unit 42 is a second-stage compression unit.

  During the cooling operation, the four-way valve 2 is switched as shown by a solid line, and the refrigerant flows in the direction of the arrow of the solid line in FIG. 1 to constitute a cooling cycle. During the cooling operation, the refrigerant compressed by the compressor 1 dissipates heat to the air in the outdoor heat exchanger 3 and condenses, and then expands and depressurizes by the first electric expansion valve 4 to condense and evaporate the pressure. The gas-liquid separator 5 separates the refrigerant into gas refrigerant and liquid refrigerant. The liquid refrigerant is further expanded and reduced in pressure by the second electric expansion valve 6, absorbs heat from the air in the indoor heat exchanger 7, evaporates, and is sucked into the compressor 1. On the other hand, the gas refrigerant separated by the gas-liquid separator passes through the injection pipe 9 and is injected into the compressor 1. In this embodiment, a compressor that performs two-stage compression, such as a two-cylinder rotary compressor, is used for the compressor 1, and the refrigerant that is compressed and discharged by the first-stage compression unit 41 is discharged from the first-stage outlet. The refrigerant is sucked into the second-stage compression section 42 through the refrigerant pipe 10 communicating with the second-stage inlet, compressed again, and discharged. The refrigerant pipe 10 is provided outside the sealed container. Note that the refrigerant pipe 10 may be referred to as an intermediate pressure space. The injection pipe 9 is connected to the refrigerant pipe 10. The injection pipe 9 is provided with an opening / closing valve 8, and the operation for performing injection and the operation for not performing the injection are switched by opening / closing the opening / closing valve 8.

  At the time of heating operation, the four-way valve 2 is switched as shown by a broken line, and the refrigerant flows in the direction of the arrow of the broken line in FIG. During the heating operation, the refrigerant compressed by the compressor 1 dissipates heat into the air in the indoor heat exchanger 7 and condenses, and then expands and depressurizes by the second electric expansion valve 6 to condense and evaporate the pressure. The gas-liquid separator 5 separates the refrigerant into gas refrigerant and liquid refrigerant. The liquid refrigerant is further expanded and depressurized by the first electric expansion valve 4, absorbs heat from the air in the outdoor heat exchanger 3, evaporates, and is sucked into the compressor 1. On the other hand, the gas refrigerant separated by the gas-liquid separator 5 passes through the injection pipe 9 and is injected into the intermediate pressure space 10 of the compressor 1. Switching between the operation that performs injection and the operation that does not perform injection by opening and closing the on-off valve 8 provided in the injection pipe 9 is the same as the cooling operation.

  The first electric expansion valve 4 and the second electric expansion valve 6 are controlled as follows. In the cooling operation, the first electric expansion valve 4 is upstream and the second electric expansion valve 6 is downstream. In heating operation, the second electric expansion valve 6 is upstream, and the first electric expansion valve 4 is downstream. Therefore, in the cooling operation, the first electric expansion valve 4 is called an upstream electric expansion valve, the second electric expansion valve 6 is called a downstream electric expansion valve, and in the heating operation, the second electric expansion valve 6 is called an upstream side. The electric expansion valve and the first electric expansion valve 4 are called downstream electric expansion valves. Based on the signal from the compressor discharge refrigerant temperature sensor 25, the control device 30 controls the upstream electric expansion valve so that the discharge refrigerant temperature becomes a predetermined value, while the first stage outlet and the second stage of the compressor. The refrigerant temperature detected by the injection refrigerant temperature sensor 23 provided in the injection pipe 9 in the vicinity of the refrigerant flow path 10 communicating with the inlet of the refrigerant, and the refrigerant pipe connecting the first electric expansion valve 4 and the gas-liquid separator 5. Based on the temperature difference from the temperature detected by the provided intermediate refrigerant temperature sensor 24, the downstream electric expansion valve 6 is controlled so that the temperature difference becomes a predetermined value. The temperature detected by the injection refrigerant temperature sensor 23 is close to the temperature at which the refrigerant from the outlet of the first stage compression unit 41 of the two-stage compressor and the refrigerant injected from the injection pipe 9 merge. The temperature detected by the intermediate refrigerant temperature sensor 24 is substantially equal to the refrigerant temperature in the gas-liquid separator 5.

  When the pressure of the refrigerant in the gas-liquid separator 5 (intermediate pressure) is low and the flow rate of the injected gas refrigerant is small, the temperature difference between these two sensors (hereinafter referred to as the temperature difference between the injection sensors) is large. As the intermediate pressure increases and the flow rate of the injected gas refrigerant increases, the temperature difference between the injection sensors decreases. When the intermediate pressure is further increased, a large amount of liquid refrigerant is injected, and the temperature difference between the injection sensors becomes close to zero.

  In the Mollier diagram of FIG. 8, the temperature of the injection refrigerant temperature sensor 23 in the broken line refrigeration cycle (ABCDEFGH) when the gas refrigerant is being injected is represented by the temperature of point C. Further, the temperature of the intermediate temperature sensor 24 is represented by the temperature at point F. As can be seen from the isotherm, the temperature at point C is higher than the temperature at point F.

  On the other hand, in the state of the solid line refrigeration cycle (A′B′C′D′E′F′G′H ′) in which a large amount of liquid refrigerant is injected, the temperature of the injection refrigerant temperature sensor 23 becomes point C ′, Since the temperature of the intermediate temperature sensor 24 becomes a point F ′, the temperature difference between the two becomes small. Conversely, when the temperature difference between the injection refrigerant temperature sensors is large, the flow rate of the refrigerant to be injected becomes small and the performance deteriorates. Therefore, as shown in FIG. 9, by controlling so that the temperature difference between the injection sensors falls within a certain range, the performance is kept high in a range where the liquid refrigerant is not injected. In the present embodiment, the intermediate temperature sensor 24 is positioned between the first electric expansion valve 4 and the gas-liquid separator 5, but between the gas-liquid separator 5 and the second electric expansion valve 6, or the injection. The pipe 9 may be provided near the gas-liquid separator 5.

  By the way, the technique described in Patent Document 1 is designed to inject liquid refrigerant by closing the two-way valve and stopping the injection regardless of the room air temperature, for example, when the outside air temperature is lower than a predetermined temperature during cooling operation. To prevent performance degradation and compressor reliability degradation.

  However, even if the outside air temperature is high in the cooling operation, if the room air temperature is high, the dryness of the refrigerant entering the gas-liquid separator 5 becomes small, and separation of the gas refrigerant becomes difficult. In the Mollier diagram of FIG. 3, the refrigeration cycle when the outside air temperature is high and the room air temperature is low is indicated by a broken line (ABCDEFGH), and the refrigeration cycle when the outside air temperature is high and the room air temperature is high is indicated by a solid line (A′B ′). C′D′E′F′G′H ′). As the indoor air temperature increases, the amount of evaporation of the indoor heat exchanger 7 acting as an evaporator increases and the pressure increases. For this reason, the state of the refrigerant entering the gas-liquid separator 5 moves from the F point to the F ′ point, and the dryness of the refrigerant is reduced. Therefore, in this case, since the dryness of the gas-liquid separator 5 is small, there is a high possibility that the liquid refrigerant will be injected, so it is necessary to stop the injection.

  On the other hand, even if the outside air temperature is low, if the indoor air temperature is low to some extent and the temperature difference between the inside and outside of the room is large, the gas refrigerant can be separated to sufficiently increase the injection effect. In the Mollier diagram of FIG. 4, the refrigeration cycle when the outside air temperature is high and the room air temperature is low is indicated by a broken line (ABCDEFGH), and the refrigeration cycle when the outside air temperature is low but the room air temperature is low is indicated by a solid line (A'B ' C′D′E′F′G′H ′). The state of the refrigerant entering each gas-liquid separator 5 is indicated by points F and F ′, but their dryness is comparable. Therefore, in this case, the gas refrigerant can be separated to sufficiently increase the injection effect.

  As described above, in Patent Document 1, since it is determined whether or not to perform the injection according to each of the outside air temperature and the indoor air temperature, the performance is reduced by injecting the liquid refrigerant, and the injection is possible. There was a problem that the performance deteriorated by stopping the injection.

  An embodiment for solving such a problem will be described below. The indoor air temperature is detected by the indoor air temperature sensor 21 of FIG. As the indoor air temperature, a temperature obtained by detecting the intake air temperature of the indoor unit may be used. In the cooling operation, the state of the refrigerant entering the gas-liquid separator 5 in the cycle (broken line ABCDEFGH) when the difference between the outside air temperature and the room air temperature is large is indicated by a point F, as shown in the Mollier diagram of FIG. On the other hand, the state of the refrigerant entering the gas-liquid separator 5 in the cycle (solid line A′B′C′D′E′F′G′H ′) when the difference between the outside air temperature and the room air temperature is small is point F. Therefore, if the difference between the outside air temperature and the room air temperature is small, the dryness of the refrigerant entering the gas-liquid separator becomes small. Therefore, the dryness of the refrigerant in the gas-liquid separator 5 becomes small and can be injected. The amount of refrigerant is reduced.

  In the Mollier diagram of FIG. 3, the refrigeration cycle when the outside air temperature is high and the room air temperature is low is indicated by a broken line (ABCDEFG), and the refrigeration cycle when the outside air temperature is high and the room air temperature is high is indicated by a solid line (A ′ B′C′D′E′F′G′H ′). As the indoor air temperature increases, the difference between the outside air temperature and the indoor air temperature decreases, and the state of the refrigerant entering the gas-liquid separator moves from the point F to the point F ′, so that the dryness of the refrigerant decreases. In such a case, a large amount of liquid refrigerant is injected, and the efficiency of the compressor 1 is greatly reduced due to vaporization of the liquid refrigerant in the suction section of the second stage (high pressure side) of the compressor 1, or the evaporator 1 There is a possibility that the flow rate of the flowing refrigerant is greatly reduced and the performance of the refrigeration cycle is deteriorated. Further, the reliability of the compressor may be lowered, for example, the lubricating oil in the compression chamber is taken away by the liquid refrigerant, resulting in poor lubrication.

  Therefore, the temperature difference between the outside air temperature and the room air temperature is obtained, and when this difference is less than a predetermined value, for example, 2 ° C. or less (cooling operation), control is performed so that the on-off valve 8 is fully closed to stop the injection. .

  In the Mollier diagram of FIG. 4, the refrigeration cycle when the outside air temperature is high and the room air temperature is low is indicated by a broken line (ABCDEFG), and the refrigeration cycle when the outside air temperature is low but the room air temperature is low is indicated by a solid line (A′B ′). C′D′E′F′G′H ′). In this example, the temperature difference between the outside air temperature and the room air temperature is about the same in any refrigeration cycle. The state of the refrigerant entering each gas-liquid separator is indicated by point F and point F ′, and their dryness is also similar. Therefore, it is possible to separate the gas refrigerant and sufficiently improve the injection effect.

  If the temperature difference between the inside and outside of the room is sufficiently large, the dryness of the refrigerant in the gas-liquid separator is kept to a certain degree or more, so that the on-off valve 8 is opened and the injection is controlled.

  FIG. 5 shows conditions for determining opening / closing of the on-off valve 8 provided in the injection circuit in accordance with the room air temperature and the outside air temperature during the cooling operation. The straight line in FIG. 5 shows a condition where the difference between the outside air temperature and the room air temperature is constant. That is, this straight line performs injection when the outside air temperature is higher than 2 ° C. above the room temperature, and does not perform injection when the temperature is 2 ° C. or lower (the on-off valve 8 is closed). The numerical value of 2 ° C. is an experimental value and may be changed according to various conditions.

  The same applies to the heating operation. When the temperature difference between the room air temperature and the outside air temperature (in the heating operation, the room air temperature is higher than the outside air temperature) is small, the dryness of the refrigerant in the gas-liquid separator 5 is small. Since the amount of gas refrigerant that can be injected is small, a large amount of liquid refrigerant is likely to be injected. Therefore, when the temperature difference between the indoor air temperature and the outdoor air temperature is a predetermined value or less, for example, 10 ° C. or less (this is also an experimental value and can be changed according to various conditions), the on-off valve 8 is fully closed to stop the injection. To control.

  FIG. 6 shows conditions for determining opening / closing of the on-off valve 8 provided in the injection circuit in accordance with the room air temperature and the outside air temperature during the heating operation. The straight line in FIG. 6 indicates a condition where the difference between the outside air temperature and the room air temperature is constant. This straight line means that the injection is performed when the indoor air temperature is higher than 10 ° C. than the outdoor air temperature, and the injection is stopped when the indoor air temperature is 10 ° C. or lower.

  FIG. 7 shows a block diagram of a control device that controls the on-off valve in accordance with the difference between the indoor air temperature and the outside air temperature. Respective temperatures are detected by the outside air temperature detection means 21 and the indoor air temperature detection means 22, and the temperature difference calculation means 51 calculates the temperature difference between them. The temperature difference and the reference value stored in the indoor / outdoor temperature difference reference value storage means 52 (2 ° C. during cooling and 10 ° C. during heating) are compared in the comparison means 53, and on-off valve driving is performed based on the result. In the means 54, the on-off valve is driven. Actually, the calculation of the temperature difference and the comparison between the temperature difference and the temperature difference reference value are performed by an arithmetic unit 31 such as a microcomputer provided in the control device 30 of FIG. It is stored in the storage device 32 provided in As described above, by controlling the on-off valve in accordance with the difference between the indoor air temperature and the outside air temperature, it is possible to prevent a decrease in performance and a decrease in the reliability of the compressor.

  If the temperature difference between the injection sensors is smaller than the predetermined value even when the downstream electric expansion valve is opened above the predetermined value, the refrigerant pressure (intermediate pressure) in the gas-liquid separator is high, and a large amount of liquid refrigerant is injected. Therefore, control to close the on-off valve 8 is performed. For example, when the distance between the indoor unit and the outdoor unit is large and the connection pipe is long, the flow resistance of the connection pipe is large, and the refrigerant pressure (intermediate pressure) in the gas-liquid separator increases during cooling operation, resulting in a large amount of liquid refrigerant. In some cases, the on-off valve 8 is closed in response to such a case. By such control, it is possible to prevent the performance from being reduced and the reliability of the compressor from being lowered due to the injection of a large amount of liquid refrigerant.

  When the discharge refrigerant temperature of the compressor is low, such as from the start of operation until the refrigeration cycle stabilizes to some extent, the upstream pressure is large, the intermediate pressure is high, and a large amount of liquid refrigerant is injected. There is. In order to avoid this, by controlling the on-off valve 8 to be closed when the refrigerant temperature detected by the compressor discharge refrigerant temperature detection means 25 in FIG. 1 is lower than the compressor discharge refrigerant temperature target value by a predetermined value or more, It is possible to prevent the deterioration of the compressor and the reliability of the compressor. The compressor discharge refrigerant temperature target value is set according to the compressor rotation speed and the outside air temperature. For example, the compressor discharge refrigerant temperature target value is calculated by a linear expression of the compressor rotation speed and the outside air temperature. The compressor discharge refrigerant temperature target value is actually set by a calculation device 31 and a storage device 32 provided in the control device 30. When the refrigeration cycle is stable, the compressor discharge refrigerant temperature is stabilized near this target value.

  The on-off valve 8 may be an electric two-way valve, but the operation is more reliable when it is an electric expansion valve that can be fully closed. In particular, in the case of a two-way valve that is used in a state where it is not energized except during switching in order to reduce power consumption, the compressor side with high pressure and the gas-liquid separator side with low pressure when the valve is closed If the differential pressure is large, the valve may open due to the differential pressure, and the refrigerant may flow backward from the compressor to the gas-liquid separator, thereby reducing the performance. By using the electric expansion valve that can be fully closed, the valve is not opened by the differential pressure, and performance degradation can be prevented.

  As a condition for closing the on-off valve 8, a difference between the refrigerant temperature of the outdoor heat exchanger and the refrigerant temperature of the indoor heat exchanger may be used instead of using the difference between the outdoor air temperature and the indoor air temperature. As shown in FIG. 10, during the cooling operation, when the difference between the outdoor heat exchanger refrigerant temperature and the indoor heat exchanger refrigerant temperature is equal to or less than a predetermined value, the on-off valve 8 is fully closed to stop the injection. Control. As shown in FIG. 11, during the heating operation, when the difference between the indoor heat exchanger refrigerant temperature and the outdoor heat exchanger refrigerant temperature is equal to or less than a predetermined value, the on-off valve 8 is fully closed to stop the injection. Control. The difference between the outdoor heat exchanger refrigerant temperature and the indoor heat exchanger refrigerant temperature serving as the reference may be set as a function of the compressor rotational speed. By performing such control, it is possible to prevent performance degradation and compressor reliability degradation.

  As described above, according to this embodiment, the gas refrigerant separated by the gas-liquid separator 5 can be fully closed provided between the gas-liquid separator 5 and the compressor 2 of the injection circuit 9 that guides the gas refrigerant to the compressor 1. When the difference between the outside air temperature detected by the open / close valve 8, the outside air temperature detecting means 21, the indoor air temperature detecting means 22, and the outside air temperature detecting means 21 and the indoor air temperature detected by the indoor air temperature 22 is equal to or less than a predetermined value. A control means 30 for fully closing the on-off valve 8 is provided. Thereby, in the cooling operation, as shown in the Mollier diagram of FIG. 2, the state of the refrigerant entering the gas-liquid separator 5 in the cycle (broken line) when the difference between the outside air temperature and the room air temperature is large is indicated by a point F. On the other hand, since the state of the refrigerant entering the gas-liquid separator 5 in the cycle (solid line) when the difference between the outside air temperature and the room air temperature is small is indicated by a point F ′, the difference between the outside air temperature and the room air temperature. If it is small, the dryness of the refrigerant entering the gas-liquid separator 5 becomes small, so that a large amount of liquid refrigerant may be mixed and injected. When a large amount of liquid refrigerant is injected, the performance of the refrigeration cycle is lowered or the reliability of the compressor is lowered, which is not desirable. Therefore, in such a case, control is performed so that the on-off valve 8 is closed and the injection is stopped. This condition also applies to the case of the solid line in FIG. 3 described above. On the other hand, when the temperature difference between the room and the outside is large as in the two refrigeration cycles shown in FIG. 4, control is performed such that the on-off valve 8 is opened to perform injection.

  In addition, the refrigerant flow that connects the two-stage compressor 2, the gas-liquid separator 5, and the gas refrigerant separated by the gas-liquid separator 5 between the first-stage outlet and the second-stage inlet in the two-stage compressor 1. In the refrigeration cycle apparatus including the injection circuit 9 that leads to the passage 10, the on-off valve 8 that is provided in the refrigerant pipe of the injection circuit 9 and can be fully closed, the first-stage outlet, and the second-stage inlet of the compressor 1 A refrigerant temperature detecting means 23 provided in the refrigerant pipe of the injection circuit 9 in the vicinity of the refrigerant flow path 10 communicating with the refrigerant pipe, a refrigerant pipe or a gas-liquid separator connecting the first expansion means and the gas-liquid separator 5, The refrigerant temperature detecting means 24 provided on either the refrigerant pipe connecting the second electric expansion valve or the refrigerant pipe of the injection circuit in the vicinity of the gas-liquid separator is detected by the two refrigerant temperature detecting means. The refrigerant temperature difference is greater than the specified value In, and opening of the expansion means of the electric expansion valve or the like on the downstream side is provided with a closing control means the opening and closing valve when the predetermined value or more. As shown in the Mollier diagram of FIG. 8, when the amount of injected liquid refrigerant increases, the state of the refrigerant on the compressor side moves from point C to point C ′ in FIG. 8, and the state of the refrigerant on the gas-liquid separator side Moves from the point F to the point F ′, the temperature difference between them tends to be small. Therefore, it is possible to detect a case where a large amount of liquid refrigerant is mixed in the refrigerant to be injected using this temperature difference. Even if the opening degree of the expansion means such as the electric expansion valve on the downstream side is equal to or greater than a predetermined value, it is considered that a large amount of liquid refrigerant is mixed when the temperature difference is equal to or smaller than the predetermined value, and the on-off valve of the injection circuit is closed. Control to stop the injection.

  The outdoor heat exchanger refrigerant temperature detecting means 21 for detecting the refrigerant temperature of the outdoor heat exchanger, the indoor heat exchanger refrigerant temperature detecting means 22 for detecting the refrigerant temperature of the indoor heat exchanger, and an injection circuit 9, an on-off valve 8 provided between the gas-liquid separator 5 and the compressor 1 that can be fully closed, the outdoor heat exchanger temperature detected by the outdoor heat exchanger refrigerant temperature detection means 21, and the chamber Control means for fully closing the on-off valve 8 when the difference between the temperature of the indoor heat exchanger refrigerant detected by the inner heat exchanger refrigerant temperature detecting means 22 is equal to or less than a predetermined value. When the difference in refrigerant temperature between the indoor heat exchanger 7 and the outdoor heat exchanger 3 is small, the difference between the high-pressure side pressure and the low-pressure side pressure in the refrigeration cycle is small, and the refrigerant in the gas-liquid separator 5 is reduced. Since the degree of dryness becomes small, there is a possibility that a large amount of liquid may be mixed and injected, so the on-off valve 8 provided in the injection circuit is closed to stop the injection.

Further, in the refrigeration cycle apparatus provided with the injection circuit 9 for guiding the gas refrigerant separated by the gas-liquid separator 5 to the compressor 1, the on-off valve 8 provided in the injection circuit 9 and capable of being fully closed, and the compressor 1 The discharge temperature detection means 25 for detecting the discharge refrigerant temperature of the compressor, the discharge temperature target value setting means for setting the target value of the discharge refrigerant temperature of the compressor 1, and the temperature detected by the discharge temperature detection means 25 is the discharge temperature target value setting. Control means for fully closing the on-off valve 8 when the temperature is lower than a predetermined value by a temperature set by the means. When the compressor discharge refrigerant temperature is low, the expansion means on the upstream side is open, so the refrigerant pressure in the gas-liquid separator is high, and there is a risk of being injected with a lot of liquid mixed, The on-off valve 8 was closed to stop the injection.
Furthermore, the on-off valve 8 provided in the injection circuit 9 is an electric expansion valve that can be fully closed. In the case of a two-way valve, when the pressure difference between the compressor side having a high pressure and the gas-liquid separator 5 side having a low pressure is large when the valve is closed, the valve opens and the gas-liquid separator 5 is opened from the compressor 1. There is a risk that the refrigerant will flow backward and the performance will deteriorate. By using an electric expansion valve that can be fully closed, the valve does not open due to differential pressure.
As described above in detail, according to the present embodiment, it is possible to prevent a decrease in performance and a decrease in the reliability of the compressor due to a large amount of liquid refrigerant being injected into the compressor. In some cases, the performance can be improved by performing injection.

It is a block diagram of the refrigerating cycle apparatus in this invention. It is a Mollier diagram which shows the difference in the refrigerating cycle by the difference in indoor-outdoor temperature difference. It is a Mollier diagram which shows the difference of the refrigerating cycle when indoor air temperature differs in the same external temperature. It is a Mollier diagram which shows the difference of the refrigerating cycle when indoor air temperature differs from outdoor temperature, but the indoor-outdoor temperature difference is relatively close. It is a figure which shows the opening / closing conditions of the on-off valve provided in the injection circuit by the outside air temperature and room air temperature at the time of air_conditionaing | cooling operation. It is a figure which shows the opening / closing conditions of the on-off valve provided in the injection circuit by the outside air temperature and indoor air temperature at the time of heating operation. It is a block diagram of the control apparatus which controls an on-off valve according to the difference of indoor air temperature and outside air temperature. It is a Mollier diagram which shows the change of the temperature difference of the two refrigerant | coolant temperature sensors provided for injection control. It is a figure which shows the relationship between a downstream electric expansion valve opening degree, and the temperature difference of two refrigerant | coolant temperature sensors. It is a figure which shows the opening / closing conditions of the on-off valve provided in the injection circuit by the outdoor heat exchanger refrigerant | coolant temperature and the indoor heat exchanger refrigerant | coolant temperature at the time of air_conditionaing | cooling operation. It is a figure which shows the open / close condition of the on-off valve provided in the injection circuit by the outdoor heat exchanger refrigerant | coolant temperature at the time of heating operation, and an indoor heat exchanger refrigerant | coolant temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Four-way valve, 3 ... Outdoor heat exchanger, 4 ... 1st expansion device, 5 ... Gas-liquid separator, 6 ... 2nd expansion device, 7 ... Indoor heat exchanger, 8 ... open / close valve, 9 ... injection piping, 21 ... outside air temperature sensor, 22 ... indoor air temperature sensor.

Claims (3)

  A refrigeration cycle in which a compressor, a four-way valve, an outdoor heat exchanger, a first expansion means, a gas-liquid separator, a second expansion means, and an indoor heat exchanger are sequentially connected by piping. And an injection pipe for introducing the refrigerant separated by the gas-liquid separator to the compressor, the entire refrigeration cycle apparatus provided in the injection pipe between the gas-liquid separator and the compressor On-off valve that can be closed, outside air temperature detecting means for detecting outside air temperature, room air temperature detecting means for detecting indoor air temperature, and detection of outside air temperature and room air temperature detected by the outside air temperature detecting means A refrigeration cycle apparatus comprising: a control unit that fully closes the on-off valve when a difference from the indoor air temperature is equal to or less than a predetermined value.   A two-stage compressor that sucks and discharges refrigerant discharged from the low-pressure side compression mechanism into the high-pressure side compression mechanism, an outdoor heat exchanger, a first expansion means with adjustable opening, a gas-liquid separator, A refrigerating cycle in which a second expansion means capable of adjusting the opening and an indoor heat exchanger are connected by piping; a gas refrigerant separated by a gas-liquid separator; and a low-pressure compression mechanism in a two-stage compressor In the refrigeration cycle apparatus provided with an injection pipe that leads to an intermediate pressure space provided between the high-pressure side compression mechanism and an on-off valve that is provided in the injection pipe and that can be fully closed, and the outdoor heat exchanger An outdoor heat exchanger refrigerant temperature detecting means for detecting the refrigerant temperature, an indoor heat exchanger refrigerant temperature detecting means for detecting the refrigerant temperature of the indoor heat exchanger, and the outdoor heat exchanger refrigerant temperature detecting means. Detected outdoor heat exchanger refrigerant temperature Refrigeration cycle and control means the difference between the detected said chamber inner heat exchanger refrigerant temperature of the chamber inner heat exchanger refrigerant temperature detection means is fully closed the opening and closing valve when the predetermined value or less and. A two-stage compressor that sucks and discharges refrigerant discharged from the low-pressure side compression mechanism into the high-pressure side compression mechanism, an outdoor heat exchanger, a first expansion means with adjustable opening, a gas-liquid separator, A refrigerating cycle in which a second expansion means capable of adjusting the opening and an indoor heat exchanger are connected by piping; a gas refrigerant separated by a gas-liquid separator; and a low-pressure compression mechanism in a two-stage compressor In a refrigeration cycle apparatus including an injection pipe that leads to an intermediate pressure space provided between the high-pressure side compression mechanism and an on-off valve that can be fully closed provided in the injection pipe, and a discharge refrigerant temperature of the compressor The discharge temperature detection means for detecting the discharge temperature, the discharge temperature target value setting means for setting the target value of the discharge refrigerant temperature of the compressor, and the temperature detected by the discharge temperature detection means is set by the discharge temperature target value setting means Predetermined than temperature Refrigeration cycle and control means for said opening and closing valve is fully closed when more low.

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