JP6010294B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner equipped with a gas injection circuit.

  As an air conditioner equipped with a conventional gas injection circuit, as shown in Patent Document 1, gas injection is performed between a compressor, a gas-liquid separator, and a compression chamber and a gas-liquid separator of these compressors. In an air conditioner having a gas injection circuit and having a valve for controlling the refrigerant flow rate in the gas injection circuit, on the basis of information inputted from the outside by a user, the opening / closing operation of the on / off valve of the gas injection circuit and the compressor Some control the number of revolutions.

  As a control method of this air conditioner, the gas injection circuit is opened, the capacity increasing operation mode performed by setting the compressor rotational speed to the rating, and the consumption performed by opening the gas injection and lowering the compressor rotational speed. There is a power reduction operation mode, and the operation mode is determined based on the difference between the set temperature set by external input and the room temperature, and the operation mode is switched.

  However, the efficiency of the compressor operation efficiency decreases regardless of whether the rotational speed is high or low relative to the maximum rotational speed of the compressor. Therefore, there is a problem in that the compressor operation efficiency is reduced by reducing the compressor rotation speed in the power consumption reduction operation mode.

  Further, as shown in Patent Document 2, a gas-liquid separator is provided in a liquid pipe between an outdoor heat exchanger and an indoor heat exchanger that are connected to a compressor having a variable compression capability so that refrigerant can be circulated. There is an air conditioner provided with a gas injection circuit for returning the gas refrigerant in the gas-liquid separator to the compressor between the compressor and the suction side of the compressor. This air conditioner controls the opening and closing of the gas injection circuit within a predetermined range with respect to the switching frequency obtained from the intersection of the refrigeration capacity performance curve when the gas injection circuit is opened and the refrigeration capacity performance curve when the gas injection circuit is closed. The compressor rotational speed control is performed such that the compressor rotational speed is lowered while the gas injection circuit is opened, and the compressor rotational speed is increased while the gas injection circuit is closed, thereby suppressing fluctuations in the refrigeration capacity.

  However, the compressor rotation speed control by gas injection ON / OFF can suppress the fluctuation of the refrigeration capacity in consideration of the efficiency curve of the compressor, while the compression is performed to suppress the fluctuation of the refrigeration capacity at the time of gas injection ON / OFF switching. There is a risk of inefficient operation by increasing or decreasing the machine speed. For example, even if the compressor rotation speed is lower than the required refrigeration capacity, the gas rotation speed is lowered when the gas injection is ON, and conversely the gas injection OFF is turned on even when the compressor rotation speed is higher than the required refrigeration capacity. In such a case, an operation such as increasing the compressor speed is performed. Accordingly, there arises a problem that the compressor operation efficiency is lowered due to excess capacity or the like.

JP 2002-162086 A Japanese Patent No. 4725387

  Accordingly, the present invention has been made to solve the above problems all at once, and in an air conditioner equipped with a gas injection circuit, the air conditioning capacity according to the required operating capacity without reducing the compressor operating efficiency. A high-efficiency refrigeration cycle that supplies

  That is, the air conditioner according to the present invention is an air conditioner having a refrigerant circuit formed by connecting a variable capacity compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger in an annular shape, and has an open / close valve. One end is connected between the expansion valve and the indoor heat exchanger, and the other end is connected to the variable displacement compressor, and gas refrigerant is injected into the compression chamber in the middle of the compression of the variable displacement compressor. An injection circuit, a performance curve data storage unit for storing compressor performance curve data indicating a compressor performance curve of the variable capacity compressor, the compressor performance curve data and the rotational speed of the variable capacity compressor A controller that acquires and controls the on-off valve and the rotational speed of the variable capacity compressor, and the control section rotates the descending slope in the compressor performance curve when the rotational speed of the variable capacity compressor is In number range Opens the on-off valve and injects a gas refrigerant into the variable displacement compressor, and the opening / closing of the variable displacement compressor is within a rotational speed range of an upward gradient in the compressor performance curve. Injection control is performed such that the valve is closed and the gas refrigerant is not injected into the variable displacement compressor.

  In such a case, based on the compressor performance curve stored in advance, the compression function force is increased by opening the injection circuit within the rotational speed range of the descending slope of the compressor performance curve, and the compressor By reducing the rotational speed, it is possible to operate in a region where the compressor efficiency is good without reducing the capacity. Further, the injection circuit is closed within the range of the rising speed of the compressor performance curve, and the compressor can be operated in a region where the compressor efficiency is high by increasing the rotational speed of the compressor.

  Here, in order to prevent a decrease in compressor performance and to prevent pressure fluctuations in the refrigerant circuit due to control switching, the control unit defines the use area of the injection control as the highest efficiency point of the compressor performance curve. It is desirable that the efficiency be within the range of 5% or more.

  Further, in order to prevent a decrease in compressor performance and to prevent pressure fluctuations in the refrigerant circuit due to control switching, the control unit determines the use range of the injection control as the maximum rotational speed in the variable displacement compressor. It is desirable that the rotation speed be within a range of 10% or more of the rotation speed movable range that is the difference between the rotation speed and the minimum rotation speed.

  In order to ensure an appropriate air conditioning capacity with respect to the air conditioning capacity required at the time of cooling, and to prevent an increase in power consumption due to excessive air conditioning capacity, the control unit sets the indoor load and the outdoor load during the cooling operation. Based on this, it is desirable to calculate the evaporation pressure of the gas refrigerant in the target indoor heat exchanger and perform the injection control so that the gas refrigerant becomes the evaporation pressure.

  In order to ensure a more appropriate air conditioning capability with respect to the air conditioning capability required at the time of cooling, and to further prevent an increase in power consumption due to excessive air conditioning capability, the control unit performs an indoor load and an When the evaporation pressure of the gas refrigerant in the target indoor heat exchanger is calculated based on the outdoor load, the injection control is performed so that the gas refrigerant becomes the evaporation pressure, and the gas refrigerant does not reach the evaporation pressure It is desirable to control the rotational speed of the variable capacity compressor.

  In order to ensure an appropriate air conditioning capacity with respect to the air conditioning capacity required at the time of heating and to prevent an increase in power consumption due to an excessive air conditioning capacity, the control unit sets the indoor load and the outdoor load during the heating operation. Based on this, it is desirable to calculate the condensation pressure of the gas refrigerant in the target indoor heat exchanger and perform the injection control so that the gas refrigerant becomes the condensation pressure.

  In order to ensure a more appropriate air conditioning capability with respect to the air conditioning capability required at the time of heating and to further prevent an increase in power consumption due to an excessive air conditioning capability, the control unit performs an indoor load and an When the condensation pressure of the gas refrigerant in the target indoor heat exchanger is calculated based on the outdoor load, the injection control is performed so that the gas refrigerant reaches the condensation pressure, and the gas refrigerant does not reach the condensation pressure It is desirable to control the rotational speed of the variable capacity compressor.

  In order to cope with a larger capacity air conditioning load, it is desirable to provide a plurality of the capacity variable compressors.

  In order to cope with various types of air conditioning loads, it is desirable to have one or more indoor heat exchangers.

  In the case of a large-capacity air-conditioning load, in order to secure an appropriate air-conditioning capability with respect to the air-conditioning capability required at the time of cooling and to prevent an increase in power consumption due to excessive air-conditioning capability, the control unit During operation, the evaporation pressure of the gas refrigerant in the target indoor heat exchanger is calculated based on the indoor load and the outdoor load, and the injection control is performed in the plurality of variable displacement compressors so that the gas refrigerant becomes the evaporation pressure. It is desirable to control the number of rotations of the plurality of variable capacity compressors, and to control the number of operating the plurality of variable capacity compressors when the evaporation pressure is not reached.

  In the case of a large-capacity air-conditioning load, in order to ensure an appropriate air-conditioning capability with respect to the air-conditioning capability required at the time of heating and to prevent an increase in power consumption due to excessive air-conditioning capability, the control unit During operation, the condensation pressure of the gas refrigerant in the target indoor heat exchanger is calculated based on the indoor load and the outdoor load, and the injection control is performed in the plurality of variable displacement compressors so that the gas refrigerant becomes the condensation pressure. It is desirable to control the number of rotations of the plurality of variable capacity compressors, and to control the number of operating the plurality of variable capacity compressors when the condensing pressure is not reached.

  In order to cope with a large-capacity air conditioning load at a lower cost, a plurality of heat source units having at least one variable capacity compressor and an outdoor heat exchanger are connected to the plurality of heat source units, What is comprised combining the 1 or several indoor unit which has a heat exchanger is desirable.

  In another configuration, the variable displacement compressor includes one or more variable capacity compressors and one or more constant speed compressors whose operating capacity does not change, and the control unit includes the injection control and the variable displacement compressor. The number of revolutions of the variable capacity compressor is controlled, and when the target pressure is not reached, the method of controlling the number of operating variable capacity compressors and the constant speed compressor is low cost and large capacity. It can cope with air conditioning load.

  According to the present invention configured as described above, based on the compressor performance curve stored in advance, the compression function force is increased by opening the injection circuit within the rotation speed range of the descending slope of the compressor performance curve. By reducing the rotational speed of the compressor, it is possible to operate in a region where the compressor efficiency is good without reducing the capacity. Further, by closing the injection circuit within the range of the rising speed of the compressor performance curve and increasing the compressor speed, it is possible to operate in a region where the compressor efficiency is good. Therefore, it is possible to realize a high-efficiency refrigeration cycle that supplies air-conditioning capacity corresponding to the required operating capacity without reducing the compressor operating efficiency.

The schematic diagram which shows the structure of the air conditioner which concerns on 1st Embodiment. The schematic diagram which shows the gas injection circuit of the air conditioner which concerns on 1st Embodiment. The schematic diagram which shows the control at the time of air conditioning of the air conditioner which concerns on 1st Embodiment. The schematic diagram which shows the control at the time of the heating of the air conditioner which concerns on 1st Embodiment. The figure which shows the structure of the compression chamber in a scroll compressor. Pressure-enthalpy diagram with and without gas injection. The compressor efficiency curve figure at the time of the high pressure of a capacity | capacitance variable type compressor. The figure which extracted the efficiency curve on pressure ratio (epsilon) 1. The flowchart figure of gas injection control. The figure which shows the high efficiency area | region calculated from the efficiency decreasing rate on a compressor efficiency curve. The figure which shows the high efficiency area | region calculated from the rotation speed movable range on a compressor efficiency curve. The figure which compared the high efficiency area | region calculated in FIG. 10, FIG. The figure which shows the air_conditioning | cooling capability and evaporation pressure at the time of changing indoor load in air_conditioning | cooling conditions. The figure which shows the heating capability at the time of changing indoor load on heating conditions, and a condensation pressure. The figure which shows the heating capability and condensing pressure when outside temperature changes in heating conditions. The schematic diagram of the air conditioner provided with the several heat-source unit which concerns on 2nd Embodiment. The figure which shows compressor capacity control at the time of connecting the two heat source units provided with the two compressors. Target evaporation pressure when the outside air temperature and the indoor load change under cooling conditions. Target condensation pressure when the outside air temperature and the indoor load change under heating conditions. The figure which shows the relationship between the driving | running state of a compressor, and injection control. The figure which shows the control method of the control valve 17. FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
The air conditioner in 1st Embodiment has the outdoor unit 101 and the indoor unit 201, as shown in FIG. 1, the liquid piping 10 and gas piping 11 which connect the outdoor unit 101 and the indoor unit 201, outdoor A control device 301 that controls each unit of the unit 101 and the indoor unit 201 is provided.

  The outdoor unit 101 has a refrigerant compression circuit L1 connected in the order of an accumulator 15, a variable capacity compressor 1, an oil separator 2, a check valve 3, and a four-way valve 4, The electric expansion valve 7 and the supercooler 8 are provided, and the heat source side circuit L2 connected to the liquid pipe 10 and the subcooler 8 and the liquid pipe 10 are branched. The electric expansion valve 9 and the electric valve 16 and a motor-operated valve 17, which is connected to the variable displacement compressor 1 and has a gas injection circuit L 3 controlled by the control device 301. A gas pipe 11 is connected to the four-way valve 4.

  The indoor unit 201 includes an electric expansion valve 12, an indoor heat exchanger 13, and an indoor blower 14.

  The control device 301 is a so-called dedicated or general-purpose computer having a CPU, a memory, an I / O channel, an output device such as a display, an input device such as a keyboard, an AD converter, and the like, according to a control program stored in the memory. By operating the CPU and its peripheral devices, each unit of the outdoor unit 101 and the indoor unit 201 is controlled and functions as the performance curve data storage unit 302 and the control unit 303 are exhibited.

  The performance curve data storage unit 302 stores in advance compressor performance curve data indicating the compressor performance curve of the variable capacity compressor 1.

  The control device 301 acquires the compressor performance curve data stored in the performance curve data storage unit 302 and the rotational speed of the variable capacity compressor 1, controls the opening and closing of the motorized valve 16 and the motorized valve 17, and The rotational speed of the variable capacity compressor 1 is controlled.

  The control performed by the control device 301 is such that the motor-operated valve 17 is closed and the motor-operated valve 16 is opened when the rotational speed of the variable capacity compressor 1 is within the rotational speed range of the descending gradient in the compressor performance curve data. Gas refrigerant is injected into the machine 1, and when the rotational speed of the variable capacity compressor 1 is within the range of the upward gradient in the compressor performance curve data, the motor-operated valve 16 is closed and the motor-operated valve 17 is opened to vary the capacity. The injection control is performed such that the gas refrigerant is not injected into the mold compressor 1.

  Next, the flow of the refrigerant in the refrigerant compression circuit L1 will be described. The refrigerant gas discharged from the plurality of variable displacement compressors 1 and the oil discharged from the variable displacement compressor 1 are separated into refrigerant and oil when passing through the oil separator 2, and separated from the oil. The refrigerant flows into the four-way valve 4 through the check valve 3.

  Next, a method for controlling the gas injection circuit L3 by the control device 301 will be described. The flow of the refrigerant in the gas injection circuit is shown in FIG. When gas injection is used, the motor-operated valve 17 is closed and the motor-operated valve 16 is opened, so that the low-pressure refrigerant branched by the downstream side of the subcooler 8 and depressurized by the motor-operated expansion valve 9 is of variable capacity type. It flows into the compressor 1. Further, the control device 301 adjusts the opening degree of the electric expansion valve 9 and controls the flow rate of the refrigerant so that the superheat degree of the refrigerant reaching the electric valve 16 satisfies the target superheat degree. Thereby, it becomes possible to control the compression function force, and it becomes possible to operate in a region where the compressor efficiency is good without causing a decrease in capacity due to a decrease in the compressor rotational speed.

  Moreover, when not using gas injection, the motor operated valve 16 is closed and the motor operated valve 17 is opened. Therefore, the low-pressure refrigerant branched downstream from the subcooler 8 and decompressed by the electric expansion valve 9 is returned to the accumulator 15 through the electric valve 17. Further, the control device 301 calculates the target superheat degree from the refrigerant temperature before passing through the supercooler 8 and reaching the liquid pipe 10, and is electrically operated so that the superheat degree of the refrigerant reaching the motor-operated valve 17 satisfies the target superheat degree. The flow rate of the refrigerant is controlled by adjusting the opening degree of the expansion valve 9. As a result, the efficiency of the compressor can be improved by improving the compressor operating efficiency and reducing the low-pressure pressure loss without using gas injection.

  Next, the flow of the refrigerant during the cooling operation is shown in FIG. During the cooling operation, the refrigerant that has passed through the four-way valve 4 flows into the heat source side circuit L2, and the refrigerant that has flowed into the outdoor heat exchanger 5 is condensed by heat exchange with outdoor air blown by the outdoor blower 6. The flow rate of the condensed refrigerant gas is controlled by the electric expansion valve 7 and passes through the supercooler 8. When the refrigerant passes through the supercooler 8, the refrigerant is supercooled by exchanging heat with the low-pressure refrigerant branched on the downstream side of the supercooler 8 and decompressed by the electric expansion valve 9. The refrigerant that has exited the supercooler 8 flows into the indoor unit 201 through the connection pipe 10.

  The refrigerant flowing into the indoor unit 201 is depressurized by the electric expansion valve 12, is controlled to an arbitrary dryness, and passes through the indoor heat exchanger 13. The indoor air blown into the indoor unit 201 by the indoor blower 14 exchanges heat with the indoor heat exchanger 13, whereby the indoor air temperature can be lowered.

  The refrigerant that has passed through the indoor unit 201 flows into the outdoor unit 101 through the gas pipe 11, passes through the four-way valve 4, and flows into the accumulator 15. The accumulator 15 has a function of separating the liquid refrigerant and the gas refrigerant, and a gas refrigerant with an appropriate superheat degree is returned to the suction port of the compressor 1 to realize a refrigeration cycle.

  Next, the flow of the refrigerant during the heating operation is shown in FIG. During the heating operation, the refrigerant that has passed through the four-way valve 4 passes through the gas pipe 11 and flows into the indoor unit 201, and the indoor air temperature is changed by heat exchange with the indoor air blown by the indoor blower 14 in the indoor heat exchanger 13. To rise. The refrigerant that has passed through the indoor heat exchanger 13 is controlled to an arbitrary degree of supercooling by the electric expansion valve 12 and flows into the outdoor unit 101 through the liquid pipe 10.

  The outdoor unit 101 branches to a heat source side circuit L2 that directly flows into the subcooler 8 and a circuit that flows into the subcooler 8 after being depressurized by the electric expansion valve 9. The refrigerant that has directly passed through the supercooler 8 is depressurized by the electric expansion valve 7, controlled to an arbitrary dryness, flows into the outdoor heat exchanger 5, and blown by the outdoor blower 6 in the outdoor heat exchanger 5. Heat exchange with outdoor air. The heat exchanged refrigerant passes through the four-way valve 4 and flows into the accumulator 15. The accumulator 15 has a function of separating the liquid refrigerant and the gas refrigerant, and a gas refrigerant with an appropriate superheat degree is returned to the suction port of the compressor 1 to realize a refrigeration cycle.

  The refrigerant flowing into the subcooler 8 after being depressurized by the electric expansion valve 9 exchanges heat with the refrigerant directly passing through the subcooler 8 in the subcooler 8, and the refrigerant flow rate is controlled by adjusting the opening of the electric expansion valve. Thus, the refrigerant after heat exchange is controlled to an arbitrary degree of superheat. As a result, the amount of refrigerant flowing to the outdoor heat exchanger 5 can be reduced, so that an efficiency improvement effect due to reduction of pressure loss can be obtained.

  Next, FIG. 5 shows the structure of the compression chamber in the scroll compressor. The refrigerant compressed in the compression chamber formed by the inside of the fixed scroll 21 and the orbiting scroll whose rotation is controlled by the electric motor is discharged from the discharge port 22. At this time, the refrigerant injected from the gas injection port 24 flows into the compression chamber intermediate portion 23, thereby enabling a two-stage compression cycle.

  FIG. 6 shows a pressure-enthalpy diagram with and without gas injection. When gas injection is used, the refrigerant is injected into the compressor intermediate portion 23 to increase the amount of refrigerant circulating inside the compressor. Therefore, when the compressor speed is fixed, the high pressure increases. Low pressure tends to decrease. As a result, an increase in the input power of the air conditioning capability occurs, and it is difficult to say that the power consumption can be reduced at this stage. However, when the compressor speed is controlled and the pressure rise is suppressed, the compressor axial force decreases in the two-stage compression with the same level of refrigeration capacity, so that the input power can be reduced and the power consumption can be reduced. be able to.

  As shown in FIG. 6, since the air-conditioning capacity can be increased as an effect of gas injection, when the air-conditioning capacity is made equal, the compressor rotation speed can be reduced when using gas injection. This is advantageous in terms of compressor efficiency when not using injection.

  FIG. 7 shows an efficiency distribution diagram of the variable capacity compressor at high pressure. FIG. 8 shows an extracted efficiency curve on the pressure ratio ε1 line of this distribution diagram. The efficiency curve distribution varies roughly depending on the characteristics, although the gradient and peak value differ depending on the motor characteristics in the compressor used, the compression chamber design value, mechanical loss, leakage loss, and the like. The efficiency curve distribution is divided into a “high efficiency area” where the efficiency is high under a certain pressure condition, and a “efficiency reduction area” where the compressor efficiency decreases due to a decrease in motor efficiency or an increase in mechanical loss as the rotational speed increases. "Increased efficiency range" where the compressor efficiency decreases due to a decrease in motor efficiency due to a decrease in rotational speed and an increase in the relative ratio of mechanical loss, etc. It is divided into.

  Increasing the compressor speed in the efficiency increasing region increases the compressor efficiency, and decreasing the compressor rotating speed in the efficiency decreasing region increases the compressor efficiency. In the high efficiency region, the compressor efficiency can be maintained high by maintaining the compressor rotation speed.

  Furthermore, the air conditioning capability can be further increased, for example, by using gas injection in the efficiency increasing region. However, if gas injection is used in the efficiency increase region, there may be an excessive air conditioning capacity with respect to the required operating capacity. Therefore, if the compressor rotation speed is decreased to adjust the air conditioning capacity, the efficiency of the compressor decreases.

  FIG. 9 shows a flowchart of the gas injection control. In order to use the gas injection effectively without reducing the efficiency of the compressor, the controller 301 stores the compressor performance curve data stored in advance and the compression during operation from the state of the gas injection OFF (step S1). The current compressor operating region is determined from the machine speed (step S2), and it is determined whether or not it is a high efficiency region (step S3). If it is not the high-efficiency region, the process proceeds to a step of determining whether the region is an efficiency-reduced region (step S8). If the region is the high-efficiency region, the process proceeds to a step of determining whether gas injection is ON (step S4). In this step S4, it is determined whether or not the gas injection is ON. If the gas injection is ON, the gas injection is maintained ON (step S7), and if the gas injection is OFF, the gas injection OFF is maintained (step S7). S5). On the other hand, in step S8, it is determined whether or not it is an efficiency reduction region. If it is not the efficiency reduction region, the gas injection OFF is maintained (step S9). If it is in the efficiency decreasing region, the gas injection is turned on (step S10). In step S6, if the gas injection OFF is maintained in step S5, the gas injection control is terminated (step S11), and if not, the process returns to step S2.

  According to the air conditioner according to the first embodiment configured as described above, a gas injection circuit is provided, the current compressor operation region is determined from the compressor performance curve data and the operating compressor speed, and the performance curve is obtained. The injection circuit is opened within the range of the lower slope of the engine, and the injection circuit is closed within the speed of the upward slope of the performance curve, so that the efficiency of the compressor can be separated from when the gas injection is used and when not used. The air conditioner can be operated to be higher. Therefore, it is possible to realize a high-efficiency refrigeration cycle that supplies air-conditioning capacity corresponding to the required operating capacity without reducing the compressor operating efficiency.

  Next, a method for selecting an efficient gas injection use region in the efficiency decrease region and the efficiency increase region will be described. The compressor efficiency curve is shown in FIG. Assuming that the efficiency reduction rate from the maximum efficiency point ηmax at this time is η1 [%], N1 ≦ N ≦ N2, which is the rotational speed region within the efficiency reduction rate η1 [%] from the intersection on the compression efficiency curve of FIG. The area can be determined. However, the smaller the efficiency reduction rate η1 [%], the faster the transition to the gas injection use cycle is. However, if the interval between N1 and N2 is too narrow, cycle fluctuations due to switching of gas injection are expected, and this is corrected by the compressor speed. In this case, the hunting phenomenon becomes remarkable. Therefore, it is necessary to determine the rotation speed region ΔN for preventing the hunting phenomenon.

A factor for determining ΔN may be selected so as to ensure a constant ratio with respect to the difference between the minimum rotation speed Nmin and the maximum rotation speed Nmax during normal operation of the compressor. On the other hand, fluctuations in the rotational speed of about 10 to 15% can occur even when the number of indoor units is not stable. ΔN can be calculated from the following equation.
ΔN = (0.10-0.15) × (Nmax−Nmin) (Formula 1)
Coefficients 0, 10 to 0.15 are regions that absorb fluctuations in the compressor operating range. The calculated N3 and N4 are shown in FIG.

  FIG. 12 compares N1 and N2 calculated from the efficiency decrease rate η1 [%] with N3 and N4 calculated from (Equation 1). When N1 ≦ N3 and N2 ≧ N4, N3 and N4 are selected as high efficiency regions. In the case of N1 ≧ N3 and N2 ≦ N4, if gas injection is used in a region where the efficiency reduction rate η1 [%] exceeds 5%, the performance improvement effect due to the injection cycle is significantly reduced. By adjusting the rotation speed control range, a more efficient cycle can be realized.

  According to the air conditioner using such a method for selecting a gas injection use region, the efficiency region can be more efficiently determined by selecting the high efficiency region from the efficiency reduction rate or the rotational speed control range as the rotational speed region for performing the gas injection. In addition to realizing a good refrigeration cycle, it is possible to prevent hunting phenomena such as pressure fluctuations due to gas injection control switching.

  Next, air conditioning capability suppression control according to the indoor load under the cooling condition will be described. FIG. 13 shows the change in evaporation pressure when the indoor load is changed from 100% → 75% → 50% → 25% in the air conditioner operating under the standard cooling conditions (outside air temperature 35 ° C., indoor temperature 27 ° C.). Show.

  When the room air temperature is kept constant, when the compressor operating capacity is determined from the set temperature and the intake air temperature by the control technology, the suction pressure decreases as the indoor operating capacity decreases, and the cooling capacity depends on the operating room load. Tend to be excessive. For this reason, it leads to the feeling of cool wind more than necessary by the fall of blowing temperature, and the increase in power consumption. On the other hand, it is possible to suppress excess capacity by adopting feedback control for the target evaporation pressure and changing the target evaporation pressure as shown in FIG. . By performing gas injection control in accordance with the target evaporation pressure, energy saving operation is possible.

  When the refrigerant pressure does not reach the target evaporating pressure with only the gas injection control with respect to the target evaporating pressure, the compressor rotational speed is adjusted so that the refrigerant pressure reaches the target evaporating pressure.

  According to such an air conditioner using air conditioning capability suppression control, during operation under cooling conditions, the evaporation pressure is set as the target pressure, feedback control is performed, and the target evaporation pressure is sequentially changed from the indoor load and the outdoor load. By performing gas injection control and compressor rotation speed control according to the target evaporation pressure, a high-efficiency refrigeration cycle that can respond to different operating capacities can be realized, and excess capacity can be suppressed.

  Next, air conditioning capability suppression control according to the indoor load under heating conditions will be described. FIG. 14 shows the change in condensation pressure when the indoor load is changed from 100% → 75% → 50% → 25% in the air conditioner operating under the standard heating conditions (outside air temperature 7 ° C., indoor temperature 20 ° C.). Show.

  When the indoor air temperature is kept constant, when the compressor operating capacity is determined from the set temperature by the control technique and the intake air temperature, there is a tendency to become excessive capacity at 75% load. Further, as shown in FIG. 15, during heating, there is a tendency that the capacity becomes excessive as the outside air temperature rises. On the other hand, the feedback control for the target condensing pressure is adopted, and the excess capacity can be suppressed by changing the target condensing pressure as shown in FIG. 19 with respect to the indoor load or the outside air temperature. . Energy-saving operation is possible by performing gas injection control in accordance with the target condensation pressure.

  When the refrigerant pressure does not reach the target condensing pressure only by the gas injection control with respect to the target condensing pressure, the compressor rotational speed is adjusted so that the refrigerant pressure reaches the target condensing pressure.

  According to such an air conditioner using air conditioning capability suppression control, in operation under heating conditions, the condensation pressure is set as the target pressure, feedback control is performed, and the target condensation pressure is sequentially changed from the indoor load and the outdoor load. By performing gas injection control and compressor rotation speed control in accordance with the target condensation pressure, a high-efficiency refrigeration cycle that can respond to different operating capacities can be realized, and excess capacity can be suppressed.

Second Embodiment
FIG. 16 shows an air conditioner when a plurality of outdoor units described in the first embodiment are connected. In order to connect a plurality of heat source units externally and use them as a single air conditioning system, it is possible to cope with an increase in the number of connected heat source units as a standard for increasing the capacity of air conditioning. There is no need to prepare multiple heat source units of different sizes, and there is a cost merit by standardizing the heat source units. In addition, since the heat source unit having a standard size and mass can be transported during construction work, confirmation and securing of the carry-in route can be facilitated. Furthermore, if a plurality of heat source units can be connected, it is possible to reduce the annual power consumption by the high-efficiency refrigeration cycle operation without limiting the air conditioning load, which is advantageous for economic merit and environmental load reduction.

  In FIG. 16, 1a, 1b, 1c, and 1d are variable capacity compressors that can be controlled at an arbitrary speed by inverter control or the like, and 1a and 1b and 1c and 1d are in the same heat source side unit. In order to evenly distribute the refrigerant branch flow and the refrigerating machine oil, it is desirable to perform an operation with the same stroke volume and close to the difference in rotational speed. The heat source units 101 and 102 are externally connected to form one refrigeration cycle. For this reason, in order to equalize the flow of refrigerant and oil at the pipe connection portion, it is desirable that the compressor circulation amount of the heat source units 101 and 102 be the same as much as possible, and the air conditioning capacity of the heat source unit 101 and the heat source unit 102 is different. If there is, the compressor circulation amount is determined according to the ratio of the air conditioning capacity. However, even in this case, if the difference in the compressor circulation amount between the heat source units becomes large, it may cause a deterioration in the distribution of the refrigerating machine oil. Therefore, the difference in the compressor circulation amount of each heat source unit falls within a certain range. Thus, it is necessary to limit the compressor capacity upper limit of the heat source unit.

  During the cooling operation, the refrigerant discharged from the compressors in the heat source side unit 101 and the heat source side unit 102 is condensed in the heat exchanger 5, and the refrigerant that has been supercooled after passing through the supercooler 8 is externally connected. It passes through the liquid pipe 10 and flows into the use side unit 201. In the usage-side unit 201, the motor-operated valve 12 is controlled according to the usage situation, whereby the refrigerant flows into the heat exchanger 13 with an arbitrary degree of superheat, and exchanges heat with the indoor air blown by the blower 14. The refrigerant discharged from the heat exchanger 13 passes through the gas pipe 11 and is distributed and flows in according to the compressor circulation amounts of the heat source units 101 and 102. The refrigerant flowing in is separated into gas and liquid by the accumulator 15 and is sucked into the compressor 1. In addition, for the usage-side unit to which the stop signal is sent, the refrigerant flow is shut off by closing the motor-operated valve 12, and heat exchange with the room air in the heat exchanger 13 is eliminated. Can be reduced.

  It is necessary to reduce the air conditioning capacity of the heat source unit 101 and the heat source unit 102 according to the usage state of the use side unit 201. At this time, when the heat exchange capacity of the heat source unit 101 is too large, the high pressure decreases excessively. The required differential pressure may not be ensured. This is also disadvantageous in terms of compressor reliability, and when the piping is long or when the height difference between the heat source unit 101 and the heat source unit 102 and the use side unit 201 is large, the refrigerant cannot be circulated, and the use side unit having a large height difference. Only 201 may cause local capacity shortage. For this reason, the heat source unit 101 and the heat source unit 102 are rotated so that the operation time is equalized, and then either the heat source unit 101 or the heat source unit 102 is stopped. Therefore, the heat exchange capacity of the plurality of heat source units as a whole is reduced to the amount necessary for the use side unit capacity, and an excessive decrease in the high pressure is prevented.

  Further, the heat source unit in operation is controlled so as to maintain the target high pressure by adjusting the air volume of the blower 6. Further, for the heat source unit in which the compressor 1 is completely stopped, the blower 6 is stopped, and the electric control valve 7 and the electric control valve 9 are closed to block the flow of high-pressure refrigerant produced by the operating heat source unit.

  During the heating operation, the refrigerant discharged from the compressors in the heat source side unit 101 and the heat source side unit 102 flows into the usage side unit 201 through the gas pipe 11. Heat exchange with room air blown by the blower 14 is performed, and the condensed refrigerant is controlled by the electric expansion valve 12 so as to maintain the degree of supercooling. The refrigerant discharged from the use side unit 201 passes through the liquid pipe 10 and is distributed and flows in according to the compressor circulation amounts of the heat source units 101 and 102. The refrigerant flowing into the heat source unit passes through the supercooler 8, is controlled to an arbitrary degree of superheat by the motor-operated valve 7, and exchanges heat with the outdoor air blown from the blower 6 by the heat exchanger 5. The heat-exchanged refrigerant is gas-liquid separated by the accumulator 15 and sucked into the compressor 1. Moreover, about the utilization side unit 201 to which the stop signal was sent, the flow of a refrigerant | coolant is interrupted | blocked by closing the electrically-driven expansion valve 12, and excess heat exchange is suppressed by stopping the air blower 14, and heating capacity is reduced. be able to.

  Although it is necessary to reduce the heating capacity of the heat source unit according to the usage state of the use side unit 201, if the heat exchange capacity of the heat source unit is too large at this time, an excessive increase in the low pressure occurs and the necessary difference If the pressure cannot be secured, the operation may be stopped due to the high pressure rise. This is disadvantageous in terms of compressor reliability as in cooling operation, and refrigerant circulation is not possible when the piping is long or the height difference between the heat source unit and the user side unit is large, and only the user side unit with a large height difference. May cause local capacity shortage. For this reason, the heat source unit 101 and the heat source unit 102 are rotated so that the operation time is equalized, and then either the heat source unit 101 or the heat source unit 102 is stopped. Therefore, the heat exchange capacity of the heat source unit is reduced to the amount necessary for the use side unit capacity, and an excessive increase in the low pressure is prevented.

  Further, the heat source unit in operation is controlled so as to maintain the target low pressure by adjusting the air volume of the blower 6. Further, for the heat source unit in which the compressor 1 is completely stopped, the blower 6 is stopped, and the electric control valve 7 and the electric control valve 9 are closed to block the flow of high-pressure refrigerant produced by the operating heat source unit.

  FIG. 17 shows compressor capacity control when two heat source units including two compressors are connected. As shown in FIG. 17, the compressor capacity is calculated based on the target operating pressure shown in FIG. 18 or 19 according to the usage side operating capacity, but is proportional to the usage side operating capacity when the indoor load such as the air condition is constant. Therefore, the compressor capacity needs to be increased. When only one heat source unit is in operation and one compressor in this heat source unit is in operation, the operating compression is increased when the predetermined increase in the number of compressors is exceeded due to an increase in the use side operation capacity. Increase the number of aircraft to two. Moreover, when the predetermined heat source unit increase capacity is exceeded due to an increase in the use side operation capacity, the operation heat source unit is increased to two units. Thereby, it respond | corresponds to the increase in the compressor capacity | capacitance by the increase in utilization side operation capacity.

  When the compressor capacity is reduced in accordance with the reduction of the use side operating capacity, the number of compressors with variable capacity is controlled by controlling the number of rotations. If this happens, reduce the number of compressors operating from 4 to 2. Also, if the heat source unit reduction capacity falls below the predetermined capacity due to the reduction of the use side operating capacity, the number of operating compressors of the heat source unit on the side that continues to operate is reduced to two, and one operating heat source unit is added. Reduce to. Further, when the use side operation capacity decreases and falls below a predetermined compressor number reduction capacity, the number of compressor operations is reduced to one. Thereby, the balance between the heat source unit capacity and the compressor circulation amount can be maintained, and a high pressure drop during cooling and a low pressure rise during heating can be prevented.

  A difference is provided between the threshold value of the compressor increase capacity and the threshold value of the compressor decrease capacity, and between the threshold value of the heat source unit increase capacity and the threshold value of the heat source unit decrease capacity. Thus, it is possible to suppress an excessive increase / decrease in the number of operating compressors and the number of operating heat source units with respect to minute use side operating capacity fluctuation.

  In the case of FIG. 14, the compressor capacity is the same and the heat source unit has the same capacity. In this case, in order to equalize the inflow of refrigerant and oil to the heat source unit, each compressor is as described above. The number of compressors in the heat source unit during operation must be the same because it is necessary to use the same number of revolutions. However, if the capacity of the heat source unit is different and the installed compressor capacity is different, depending on the operating capacity ratio Thus, for example, the heat source unit in which two compressors are operating and the heat source unit in which one compressor is operating may be operated simultaneously. Also in this case, it is possible to easily control the required compressor capacity by setting the respective heat source unit increase / decrease thresholds.

  FIG. 17 shows the case where the plurality of compressors are all variable capacity compressors, with one unit being a variable capacity type and the rest being a constant speed type compressor, and the rotation speed of the variable capacity compressor and the constant speed type. It is possible to control the number of operating compressors in a similar manner.

  FIG. 20 shows the control of the motor-operated valve 16 and the motor-operated valve 17 for the operating state of the compressor and the gas injection control. When a plurality of compressors are provided in one heat source unit, the number of operating compressors increases or decreases. Therefore, it is necessary to control the electric valve 16 for gas injection corresponding to each compressor.

  The symbols in FIG. 20 correspond to the symbols in FIG. 16, and the compressor 1a and the electric valve 16a, and the compressor 1b and the electric valve 16b are connected by piping. When both the compressor 1a and the compressor 1b are stopped, since the heat source unit 101 is stopped, the motor-operated valves 16a and 16b are closed. When both the compressor 1a and the compressor 1b are operating, a gas injection ON / OFF signal is transmitted according to the control of FIG. 9, and the motor-operated valves 16a and 16b are opened and closed. When either the compressor 1a or the compressor 1b is stopped, the motor-operated valve 19 connected to the stopped compressor is always closed, and only the motor-operated valve 19 connected to the operating compressor is controlled to open and close. The

  FIG. 21 shows the control of the electric valve 16 for gas injection and the electric valve 17 for switching control. The motor-operated valve 17 is controlled by looking at the open / closed state of the motor-operated valve 16. If any of the gas injection motor-operated valves 16 in the same heat source unit is open, the motor-operated valve 17 is closed. Only when the motor-operated valve 19 is closed, the transmission valve 20 is opened.

  According to the air conditioner according to the second embodiment configured as described above, in a multi-type air conditioning system in which a plurality of heat source units are externally connected to construct a single air conditioning system, the operation of the plurality of usage-side units 201 is performed. When controlling the capacity of multiple compressors that have injection circuits according to the situation, it is possible to perform energy-saving operation with high compressor efficiency and reduce annual power consumption without limiting the load capacity on the user side. It is suitable for realizing reduction of environmental load.

<Other modified embodiments>
The present invention is not limited to the above embodiment. For example, when the use side operating capacity is small, the number of variable capacity compressors in the first embodiment may be one, or the number of indoor units may be one depending on the situation on the use side.

  In the first embodiment, one of the compressors in the outdoor unit may be a variable capacity compressor and the other may be a constant speed compressor.

  In addition, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

100 ... Air conditioner 101 ... Outdoor unit (heat source side unit)
201 ... Indoor unit (use side unit)
DESCRIPTION OF SYMBOLS 1 ... Compressor 2 ... Oil separator 3 ... Check valve 4 ... Four-way valve 5 ... Outdoor heat exchanger 6 ... Outdoor blower 7 ... Electric expansion valve 8 ... -Supercooler 9 ... Electric expansion valve 10 ... Liquid piping 11 ... Gas piping 12 ... Electric expansion valve 13 ... Indoor heat exchanger 14 ... Indoor fan 15 ... Accumulator 16・ ・ ・ Motorized valve 17 ・ ・ ・ Motorized valve 21 ・ ・ ・ Fixed scroll 22 ・ ・ ・ Discharge port 23 ・ ・ ・ Compression chamber intermediate part 24 ・ ・ ・ Injection port 102 ・ ・ ・ Outdoor unit (heat source side unit)
301 ... Control device 302 ... Performance curve data storage unit 303 ... Control unit L1 ... Refrigerant compression circuit L2 ... Heat source side circuit L3 ... Injection circuit

Claims (16)

An air conditioner having a refrigerant circuit formed by annularly connecting a variable capacity compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger,
An open / close valve, one end of which is connected between the expansion valve and the indoor heat exchanger, the other end of which is connected to the variable capacity compressor, and gas refrigerant is being compressed by the variable capacity compressor. An injection circuit that injects into the compression chamber;
A performance curve data storage unit for storing compressor performance curve data indicating a compressor performance curve of the variable capacity compressor;
A controller that acquires the compressor performance curve data and the rotational speed of the variable capacity compressor to control the rotational speed of the on-off valve and the variable capacity compressor;
In the efficiency drop region where the rotational speed of the variable capacity compressor is greater than a first threshold value and falls within a rotational speed range of a descending slope in the compressor performance curve, the control unit opens the on-off valve, and Gas refrigerant is injected into the variable capacity compressor, and the opening and closing of the variable capacity compressor is performed in an efficiency increasing region where the rotational speed of the variable capacity compressor is smaller than a second threshold value and within the rotational speed range of the rising slope in the compressor performance curve. In a high efficiency region where the valve is closed and gas refrigerant is not injected into the variable displacement compressor, and the rotational speed of the variable displacement compressor is within the rotational speed range of the first threshold value or less and the second threshold value or more. , Perform injection control to maintain the current gas refrigerant injection state,
The controller calculates the evaporation pressure of the gas refrigerant in the target indoor heat exchanger based on the indoor load and the outdoor load during the cooling operation, and performs the injection control so that the gas refrigerant becomes the evaporation pressure. Air conditioner characterized by.   2. The air conditioner according to claim 1, wherein the control unit sets a use region of the injection control to be in a range equal to or more than a region where the efficiency drops by 5% from a maximum efficiency point of the compressor performance curve.   The said control part makes the use area | region of the said injection control in the range of 10% or more of the rotational speed movable range which is a difference of the maximum rotational speed and the minimum rotational speed in the said capacity | capacitance variable compressor. Air conditioner. The control unit calculates the evaporation pressure of the gas refrigerant in the target indoor heat exchanger based on the indoor load and the outdoor load during the cooling operation, and performs the injection control so that the gas refrigerant becomes the evaporation pressure, The air conditioner according to claim 1, 2, or 3, wherein when the gas refrigerant does not reach the evaporation pressure, the rotational speed of the variable capacity compressor is controlled.   The controller calculates the condensation pressure of the gas refrigerant in the target indoor heat exchanger based on the indoor load and the outdoor load during the heating operation, and performs the injection control so that the gas refrigerant becomes the condensation pressure. The air conditioner according to claim 1, 2, or 3. The controller calculates the condensation pressure of the gas refrigerant in the target indoor heat exchanger based on the indoor load and the outdoor load during the heating operation, and performs the injection control so that the gas refrigerant becomes the condensation pressure, 6. The air conditioner according to claim 1, wherein when the gas refrigerant does not reach the condensing pressure, the rotational speed of the variable capacity compressor is controlled. The air conditioner according to claim 1, wherein a plurality of the variable capacity compressors are provided. The air conditioner according to claim 7 , comprising one or more indoor heat exchangers. The controller calculates the evaporation pressure of the gas refrigerant in the target indoor heat exchanger based on the indoor load and the outdoor load during the cooling operation, and the plurality of capacity variable types so that the gas refrigerant becomes the evaporation pressure. In the compressor, the injection control and the rotational speed control of the plurality of variable capacity compressors are performed, and further, the number of operating the plurality of variable capacity compressors is controlled when the evaporation pressure is not reached. The air conditioner according to claim 7 or 8 . The controller calculates the condensation pressure of the gas refrigerant in the target indoor heat exchanger based on the indoor load and the outdoor load during the heating operation, and the plurality of capacity variable types so that the gas refrigerant becomes the condensation pressure. In the compressor, the injection control and the rotation speed of the plurality of variable capacity compressors are controlled. Further, when the condensing pressure is not reached, the operation number of the plurality of variable capacity compressors is controlled. The air conditioner according to claim 7 or 8, characterized in that A plurality of heat source units having at least one variable capacity compressor and an outdoor heat exchanger;
The air conditioner according to claim 7, 8, 9 or 10 , wherein the air conditioner is configured by combining one or a plurality of indoor units connected to the plurality of heat source units and having an indoor heat exchanger. One or more variable capacity compressors;
One or a plurality of constant speed compressors whose operating capacity does not change,
The control unit performs the injection control and the rotational speed control of the variable capacity compressor in the variable capacity compressor, and further, when the target pressure is not reached, the variable capacity compressor and the constant speed type The air conditioner according to claim 1 , wherein the number of operating compressors is controlled. An air conditioner having a refrigerant circuit formed by annularly connecting a variable capacity compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger,
An open / close valve, one end of which is connected between the expansion valve and the indoor heat exchanger, the other end of which is connected to the variable capacity compressor, and gas refrigerant is being compressed by the variable capacity compressor. An injection circuit that injects into the compression chamber;
A performance curve data storage unit for storing compressor performance curve data indicating a compressor performance curve of the variable capacity compressor;
A controller that acquires the compressor performance curve data and the number of revolutions of the variable capacity compressor and controls the on-off valve and the variable capacity compressor;
In the efficiency drop region where the rotational speed of the variable capacity compressor is greater than a first threshold value and falls within a rotational speed range of a descending slope in the compressor performance curve, the control unit opens the on-off valve, and Gas refrigerant is injected into the variable capacity compressor, and the opening and closing of the variable capacity compressor is performed in an efficiency increasing region where the rotational speed of the variable capacity compressor is smaller than a second threshold value and within the rotational speed range of the rising slope in the compressor performance curve. In a high efficiency region where the valve is closed and gas refrigerant is not injected into the variable displacement compressor, and the rotational speed of the variable displacement compressor is within the rotational speed range of the first threshold value or less and the second threshold value or more. , Perform injection control to maintain the current gas refrigerant injection state,
The control unit calculates the evaporation pressure of the gas refrigerant in the target indoor heat exchanger based on the indoor load and the outdoor load during the cooling operation, and performs the injection control so that the gas refrigerant becomes the evaporation pressure. Is provided with a computer. An air conditioner having a refrigerant circuit formed by annularly connecting a variable capacity compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger,
An open / close valve, one end of which is connected between the expansion valve and the indoor heat exchanger, the other end of which is connected to the variable capacity compressor, and gas refrigerant is being compressed by the variable capacity compressor. An injection circuit that injects into the compression chamber;
A performance curve data storage unit for storing compressor performance curve data indicating a compressor performance curve of the variable capacity compressor;
A controller that acquires the compressor performance curve data and the rotational speed of the variable capacity compressor to control the rotational speed of the on-off valve and the variable capacity compressor;
The controller opens the on-off valve and injects gas refrigerant into the variable displacement compressor when the rotational speed of the variable displacement compressor is within the range of the descending gradient in the compressor performance curve. When the rotational speed of the variable capacity compressor is within the rotational speed range of the upward gradient in the compressor performance curve, injection control is performed such that the open / close valve is closed and gas refrigerant is not injected into the variable capacity compressor,
The controller calculates the evaporation pressure of the gas refrigerant in the target indoor heat exchanger based on the indoor load and the outdoor load during the cooling operation, and performs the injection control so that the gas refrigerant becomes the evaporation pressure. Air conditioner characterized by. An air conditioner having a refrigerant circuit formed by annularly connecting a variable capacity compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger,
An open / close valve, one end of which is connected between the expansion valve and the indoor heat exchanger, the other end of which is connected to the variable capacity compressor, and gas refrigerant is being compressed by the variable capacity compressor. An injection circuit that injects into the compression chamber;
A performance curve data storage unit for storing compressor performance curve data indicating a compressor performance curve of the variable capacity compressor;
A controller that acquires the compressor performance curve data and the rotational speed of the variable capacity compressor to control the rotational speed of the on-off valve and the variable capacity compressor;
The controller opens the on-off valve and injects gas refrigerant into the variable displacement compressor when the rotational speed of the variable displacement compressor is within the range of the descending gradient in the compressor performance curve. When the rotational speed of the variable capacity compressor is within the rotational speed range of the upward gradient in the compressor performance curve, injection control is performed such that the open / close valve is closed and gas refrigerant is not injected into the variable capacity compressor,
The controller calculates the condensation pressure of the gas refrigerant in the target indoor heat exchanger based on the indoor load and the outdoor load during the heating operation, and performs the injection control so that the gas refrigerant becomes the condensation pressure. Air conditioner characterized by. An air conditioner having a refrigerant circuit formed by annularly connecting a variable capacity compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger,
An open / close valve, one end of which is connected between the expansion valve and the indoor heat exchanger, the other end of which is connected to the variable capacity compressor, and gas refrigerant is being compressed by the variable capacity compressor. An injection circuit that injects into the compression chamber;
A performance curve data storage unit for storing compressor performance curve data indicating a compressor performance curve of the variable capacity compressor;
A controller that acquires the compressor performance curve data and the rotational speed of the variable capacity compressor to control the rotational speed of the on-off valve and the variable capacity compressor;
The controller opens the on-off valve and injects gas refrigerant into the variable displacement compressor when the rotational speed of the variable displacement compressor is within the range of the descending gradient in the compressor performance curve. When the rotational speed of the variable capacity compressor is within the rotational speed range of the upward gradient in the compressor performance curve, injection control is performed such that the open / close valve is closed and gas refrigerant is not injected into the variable capacity compressor,
A plurality of the variable capacity compressors;
The controller calculates the evaporation pressure of the gas refrigerant in the target indoor heat exchanger based on the indoor load and the outdoor load during the cooling operation, and the plurality of capacity variable types so that the gas refrigerant becomes the evaporation pressure. In the compressor, the injection control and the rotational speed control of the plurality of variable capacity compressors are performed, and further, the number of operating the plurality of variable capacity compressors is controlled when the evaporation pressure is not reached. Air conditioner.