JP2009229012A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve operation efficiency of a refrigerating device by reducing the number of times of start and stop of a compressor, in the refrigerating device performing so-called supercritical cycle. <P>SOLUTION: An air conditioner 10 composed of this refrigerating device is provided with a main controller 60 and sub-controllers 70a, 70b. A compressor control section of the main controller 60 adjusts an operation capacity of the compressor 31, and stops the compressor 31 when a capacity of the air conditioner 10 becomes excessive to a load. When the frequency of start and stop of the compressor 31 by the compressor control section is increased, a superheat degree target value changing section of the main controller 60 forcibly raises a superheat degree target value. Then the sub-controllers 70a, 70b adjust openings of indoor expansion valves 42, 47 by using the raised superheat degree target value in a cooling operation. The main controller 60 adjusts an opening of an outdoor expansion valve 34 on the basis of the raised superheat degree target value in a heating operation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus that performs a refrigeration cycle in which a high pressure is set to a value higher than a critical pressure of a refrigerant.

  Conventionally, a refrigeration apparatus that performs a refrigeration cycle by circulating a refrigerant in a refrigerant circuit is known. In the refrigeration apparatus disclosed in Patent Document 1, the high pressure of the refrigeration cycle performed in the refrigerant circuit is set to a value higher than the critical pressure of the refrigerant. That is, a so-called supercritical cycle is performed in the refrigerant circuit of the refrigeration apparatus.

Moreover, in the air conditioning apparatus disclosed in Patent Document 2, a general refrigeration cycle in which the high pressure is set to a value lower than the critical pressure of the refrigerant is performed. In the air conditioner of Patent Document 2, the target value for controlling the operation of the air conditioner is adjusted in order to reduce the frequency of starting and stopping of the compressor.
JP 2001-116376 A JP 2002-061925 A

  By the way, even in a refrigeration apparatus that performs a so-called supercritical cycle, the compressor may be started and stopped in order to adjust the capacity of the refrigeration apparatus. For example, even if the compressor is a variable capacity type, the capacity of the refrigeration system may be too large for the load even if the capacity of the compressor is minimized. In such a situation, the compressor is stopped. It is done.

  In the supercritical cycle, the high pressure is higher than in a general refrigeration cycle. For this reason, in comparison with a general refrigeration cycle in which the high pressure is lower than the critical pressure of the refrigerant, in the refrigeration system that performs the supercritical cycle, the high pressure and low pressure of the refrigeration cycle reach appropriate values after starting the compressor. The power required for this increases. Nevertheless, until now, sufficient measures have not been taken to reduce the frequency of start and stop of the compressor in a refrigeration apparatus that performs a supercritical cycle.

  The present invention has been made in view of the above points, and an object of the present invention is to improve the operating efficiency of the refrigeration apparatus by reducing the number of times the compressor is started and stopped in a refrigeration apparatus that performs a so-called supercritical cycle. .

  In the first invention, the compressor (31), the expansion mechanism (34, 42, 47), the heat source side heat exchanger (33), and the use side heat exchanger (41, 46) are connected, and the high pressure is the refrigerant. A refrigerant circuit (20) for performing a refrigeration cycle set to a value higher than the critical pressure, and a control means (80) for controlling the compressor (31) and the expansion mechanism (34, 42, 47) are provided. For refrigeration equipment. And the said control means (80) is a capacity | capacitance control operation | movement which adjusts the capacity | capacitance of the said compressor (31) so that the physical quantity which shows the operation state of the refrigerating cycle performed by the said refrigerant circuit (20) becomes a control target value. And the degree of superheat of the refrigerant from the heat source side heat exchanger (33) and the use side heat exchanger (41, 46) operating as an evaporator to the compressor (31) is the superheat degree target value. When the compressor (31) is stopped by the flow rate control operation for adjusting the flow rate of the refrigerant passing through the expansion mechanism (34, 42, 47) and the capacity control operation, the degree of superheat The superheat degree target value changing operation for forcibly raising the target value is performed.

  In the second invention, the compressor (31), the expansion mechanism (34, 42, 47), the heat source side heat exchanger (33), and the use side heat exchanger (41, 46) are connected, and the high pressure is the refrigerant. A refrigerant circuit (20) for performing a refrigeration cycle set to a value higher than the critical pressure, and a control means (80) for controlling the compressor (31), wherein the heat source side heat exchanger (33) A refrigeration apparatus that operates as a gas cooler and performs at least a cooling operation in which the use side heat exchanger (41, 46) operates as an evaporator is an object. The control means (80) uses the evaporation temperature of the refrigerant in the use side heat exchanger (41, 46) or the low pressure of the refrigeration cycle performed in the refrigerant circuit (20) as a control parameter. A capacity control operation for adjusting the capacity of the compressor (31) so as to be a control target value, and the control target value becomes a predetermined standard target value after a predetermined time has elapsed since the start of the compressor (31). As described above, the control target value changing operation for gradually decreasing the control target value after the start of the compressor (31) is performed.

  In the third invention, the compressor (31), the expansion mechanism (34, 42, 47), the heat source side heat exchanger (33), and the use side heat exchanger (41, 46) are connected, and the high pressure is the refrigerant. A refrigerant circuit (20) for performing a refrigeration cycle set to a value higher than the critical pressure; and a control means (80) for controlling the compressor (31), the utilization side heat exchanger (41, 46) ) Is operated as a gas cooler, and the refrigeration apparatus performing at least the heating operation in which the heat source side heat exchanger (33) operates as an evaporator is an object. The control means (80) uses the high pressure of the refrigeration cycle performed in the refrigerant circuit (20) as a control parameter, and adjusts the capacity of the compressor (31) so that the control parameter becomes a control target value. The control target value is gradually set after starting the compressor (31) so that the control target value becomes a predetermined standard target value after a predetermined time has elapsed since the start of the compressor (31). The control target value changing operation is increased.

  In the fourth aspect of the invention, the compressor (31), the expansion mechanism (34, 42, 47), the heat source side heat exchanger (33), and the use side heat exchanger (41, 46) are connected, and the high pressure is the refrigerant. A refrigeration apparatus including a refrigerant circuit (20) that performs a refrigeration cycle set to a value higher than the critical pressure and a control means (80) that controls the compressor (31) is an object. Then, the control means (80) sets the command value calculated using the physical quantity and the control gain so that the physical quantity indicating the operating state of the refrigeration cycle performed in the refrigerant circuit (20) becomes a control target value. Based on this, a capacity control operation for adjusting the capacity of the compressor (31) and a gain adjustment operation for reducing the control gain as the load of the refrigeration apparatus decreases are configured.

  In each of the first, second, third and fourth inventions, a refrigeration cycle is performed by circulating refrigerant in the refrigerant circuit (20). At that time, the pressure of the refrigerant discharged from the compressor (31) is higher than the critical pressure of the refrigerant. Further, one of the heat source side heat exchanger (33) and the use side heat exchanger (41, 46) provided in the refrigerant circuit (20) operates as a gas cooler, and the other operates as an evaporator.

  In the first invention, the control means (80) performs a capacity control operation. In this capacity control operation, the capacity of the compressor (31) is adjusted so that the predetermined physical quantity becomes the control target value. The control means (80) stops the compressor (31) when the predetermined physical quantity deviates from the control target value but the capacity of the compressor (31) cannot be reduced any more. When the compressor (31) is stopped by the capacity control operation, the control means (80) performs the superheat degree target value changing operation and forcibly raises the superheat degree target value. Thereafter, when the operation of the compressor (31) is resumed, the control means (80) performs a flow rate control operation using the superheat degree target value raised by the superheat degree target value changing operation. In other words, the control means (80) expands so that the superheat degree of the refrigerant heading from the heat exchanger (33, 41, 46) operating as an evaporator to the compressor (31) becomes the superheat degree target value raised. The flow rate of the refrigerant passing through the mechanism (34, 42, 47) is adjusted.

  In the first invention, the expansion mechanism (34, 42, 47) is set to a state where the flow rate of the refrigerant passing therethrough decreases as the superheat degree target value increases. Compared with the case where the capacity of the compressor (31) is the same, the higher the superheat degree target value, the smaller the amount of refrigerant circulating in the refrigerant circuit (20), so the capacity of the refrigeration apparatus (10) becomes lower. That is, the lower the superheat degree target value, the lower the lower limit value of the capacity of the refrigeration apparatus (10). For this reason, even if the control means (80) had to stop the compressor (31) before raising the target superheat, the compressor (31) continued to operate after raising the target superheat. The possibility of being able to be increased.

  In the second invention, the control means (80) performs a capacity control operation and a control target value changing operation during the cooling operation. In this capacity control operation, the control means (80) uses the refrigerant evaporation temperature in the use side heat exchanger (41, 46) or the low pressure of the refrigeration cycle performed in the refrigerant circuit (20) as a control parameter. The capacity of the compressor (31) is adjusted so as to reach the control target value. The control means (80) stops the compressor (31) when the capacity of the compressor (31) cannot be further reduced even though the control parameter deviates from the control target value. Thereafter, when the operation of the compressor (31) is resumed, the control means (80) performs a control target value changing operation. In this control target value changing operation, the control means (80) sets the control target value at the time when the operation of the compressor (31) is resumed to a value higher than the standard target value, and a predetermined time has elapsed from that point. In the meantime, the control target value is gradually lowered to approach the standard target value. Meanwhile, in the capacity control operation, the capacity adjustment of the compressor (31) is performed using the control target value adjusted by the control target value changing operation.

  Here, immediately after the compressor (31) is started, the difference between the measured value of the refrigerant evaporation temperature and the low pressure of the refrigeration cycle, which are control parameters, and the standard target value is large. Therefore, if the control target value remains at the standard target value immediately after the compressor (31) is started, the capacity of the compressor (31) increases rapidly in order to bring the control parameter close to the standard target value as soon as possible. Will be allowed to. And if the cooling capacity of the refrigeration system (10) suddenly increases with the rapid capacity increase of the compressor (31), the cooling capacity will be excessive in a relatively short time after the compressor (31) is started. Thus, the compressor (31) must be stopped again.

  In contrast, the control means (80) of the second invention sets the control target value to a value higher than the standard target value for a while after the compressor (31) is started. Therefore, even immediately after the compressor (31) is started, the control target value remains the standard target value in terms of the difference between the measured value of the evaporation temperature of the refrigerant and the low pressure of the refrigeration cycle and the control target value. Smaller than in some cases. As a result, the rapid increase in capacity of the compressor (31) after the start of the compressor (31) is suppressed, and the cooling capacity of the refrigeration apparatus (10) also changes gradually. Therefore, when the control means (80) makes the control target value higher than the standard target value as in the present invention, the control means (80) stops the compressor (31) if the control target value remains the standard target value. There is a high possibility that the operation of the compressor (31) can be continued even in a situation where it has been necessary to do so.

  In the third invention, the control means (80) performs a capacity control operation and a control target value changing operation during the heating operation. In this capacity control operation, the control means (80) uses the high pressure of the refrigeration cycle performed in the refrigerant circuit (20) as a control parameter, and adjusts the capacity of the compressor (31) so that the control parameter becomes a control target value. . The control means (80) stops the compressor (31) when the capacity of the compressor (31) cannot be further reduced even though the control parameter deviates from the control target value. Thereafter, when the operation of the compressor (31) is resumed, the control means (80) performs a control target value changing operation. In this control target value changing operation, the control means (80) sets the control target value at the time when the operation of the compressor (31) is resumed to a value lower than the standard target value, and a predetermined time has elapsed from that point. In the meantime, the control target value is gradually raised to approach the standard target value. Meanwhile, in the capacity control operation, the capacity adjustment of the compressor (31) is performed using the control target value adjusted by the control target value changing operation.

  Here, immediately after the compressor (31) is started, the difference between the measured value of the high pressure of the refrigeration cycle, which is a control parameter, and the standard target value is large. Therefore, if the control target value remains at the standard target value immediately after the compressor (31) is started, the capacity of the compressor (31) increases rapidly in order to bring the control parameter close to the standard target value as soon as possible. Will be allowed to. And if the heating capacity of the refrigeration system (10) increases rapidly with the sudden increase in capacity of the compressor (31), the heating capacity will be excessive in a relatively short time after the compressor (31) is started. Thus, the compressor (31) must be stopped again.

  In contrast, the control means (80) of the third invention sets the control target value to a value lower than the standard target value for a while after the compressor (31) is started. Therefore, even immediately after the compressor (31) is started, the difference between the measured value of the high pressure of the refrigeration cycle, which is the control parameter, and the control target value is compared with the case where the control target value remains the standard target value. Get smaller. As a result, the rapid capacity increase of the compressor (31) after the start of the compressor (31) is suppressed, and the heating capacity of the refrigeration apparatus (10) also changes gradually. For this reason, if the control means (80) makes the control target value lower than the standard target value as in the present invention, the control means (80) stops the compressor (31) if the control target value remains the standard target value. There is a high possibility that the operation of the compressor (31) can be continued even in a situation where it has been necessary to do so.

  In the fourth invention, the control means (80) performs the capacity control operation and the control target value changing operation. In this capacity control operation, the capacity of the compressor (31) is adjusted so that the predetermined physical quantity becomes the control target value. The control means (80) stops the compressor (31) when the predetermined physical quantity deviates from the control target value but the capacity of the compressor (31) cannot be reduced any more. On the other hand, the control means (80) performs a gain adjustment operation, and decreases the value of the control gain used in the capacity control operation as the load on the refrigeration apparatus (10) decreases.

  Here, if the control gain remains high even though the load of the refrigeration apparatus (10) is small, the change in the capacity of the compressor (31) determined based on the deviation between the predetermined physical quantity and the control target value The amount will increase. As a result, the capacity of the refrigeration apparatus (10) becomes excessive with respect to the load, and there is a high possibility that the compressor (31) must be stopped.

  In contrast, the control means (80) of the fourth aspect of the invention reduces the value of the control gain as the load on the refrigeration apparatus (10) decreases. As a result, the command value calculated using the predetermined physical quantity and the control gain is smaller than that when the control gain is constant. For this reason, when the control means (80) reduces the control gain as in the present invention, the control means (80) must stop the compressor (31) if the control gain remains constant. The possibility that the operation of the compressor (31) can be continued increases.

  As described above, in the first invention, the capacity of the refrigeration apparatus (10) is excessive with respect to the load by increasing the superheat degree target value and lowering the lower limit value of the capacity of the refrigeration apparatus (10). This reduces the possibility of the compressor (31) stopping due to the failure. In the second aspect of the invention, the cooling capacity of the refrigeration apparatus (10) becomes excessive with respect to the load by setting the control parameter during the cooling operation to a higher value immediately after the compressor (31) is started. This reduces the possibility that the compressor (31) will stop. Moreover, in the said 3rd invention, the heating capability of the freezing apparatus (10) became excessive with respect to load by setting the control parameter in heating operation low immediately after starting of a compressor (31). This reduces the possibility that the compressor (31) will stop. In the fourth aspect of the invention, when the load of the refrigeration apparatus (10) is small, the control gain is set to be small, thereby causing the capacity of the refrigeration apparatus (10) to be excessive with respect to the load. This reduces the possibility of the compressor (31) stopping.

  Thus, according to the present invention, in the refrigeration apparatus (10) performing a so-called supercritical cycle, the compressor (31) is caused by the fact that the capacity of the refrigeration apparatus (10) is excessive with respect to the load. The possibility of stopping can be reduced. In other words, capacity adjustment in the refrigeration system (10) that performs the supercritical cycle with the characteristic that “the power required for the high pressure and low pressure of the refrigeration cycle to reach appropriate values after starting the compressor (31) increases” Therefore, the number of times the compressor (31) starts and stops can be reduced. Therefore, according to the present invention, the power consumed during the operation of the refrigeration apparatus (10) can be reduced by reducing the number of times the compressor (31) for adjusting the capacity is started and stopped, and the refrigeration apparatus (10) The driving efficiency can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Each embodiment described below is an air conditioner (10) configured by a refrigeration apparatus.

Embodiment 1 of the Invention
As shown in FIG. 1, the air conditioner (10) of this embodiment is provided with one outdoor unit (11) and two indoor units (12, 13). The outdoor unit (11) is installed outdoors. Each indoor unit (12, 13) is installed indoors. The number of outdoor units (11) and indoor units (12, 13) shown here is merely an example. The air conditioner (10) includes a main controller (60) and sub controllers (70a, 70b). The main controller (60) and the sub-controllers (70a, 70b) constitute control means (80).

In the air conditioner (10) of the present embodiment, the outdoor circuit (30) of the outdoor unit (11) and the indoor circuit (40, 45) of each indoor unit (12, 13) are connected to the liquid side communication pipe (21) and The refrigerant circuit (20) is formed by connecting with the gas side connecting pipe (22). The refrigerant circuit (20) is filled with carbon dioxide (CO ₂ ) as a refrigerant. In the refrigeration cycle performed in the refrigerant circuit (20), the high pressure is set to a value higher than the critical pressure of carbon dioxide, which is a refrigerant.

  One outdoor circuit (30) is accommodated in the outdoor unit (11). The outdoor circuit (30) includes a compressor (31), a four-way switching valve (32), an outdoor heat exchanger (33) that is a heat source side heat exchanger, and an outdoor expansion valve (34) that is an expansion mechanism. A receiver (35), a liquid side closing valve (36), and a gas side closing valve (37) are provided. The outdoor unit (11) is provided with an outdoor fan (16) for sending outdoor air to the outdoor heat exchanger (33).

  In the outdoor circuit (30), the compressor (31) has its discharge side connected to the first port of the four-way switching valve (32) and its suction side connected to the second port of the four-way switching valve (32). Yes. The outdoor heat exchanger (33) has a gas side end connected to the third port of the four-way switching valve and a liquid side end connected to one end of the outdoor expansion valve (34). The other end of the outdoor expansion valve (34) is connected to the liquid side closing valve (36) via the receiver (35). The fourth port of the four-way switching valve (32) is connected to the gas side closing valve (37).

  Each indoor unit (12, 13) accommodates one indoor circuit (40, 45). Each indoor circuit (40, 45) is connected to an indoor heat exchanger (41, 46) which is a use side heat exchanger and an indoor expansion valve (42, 47) which is an expansion mechanism. . In each indoor circuit (40, 45), the indoor heat exchanger (41, 46) and the indoor expansion valve (42, 47) are arranged in series. Each indoor unit (12, 13) is provided with one indoor fan (17, 18) for sending indoor air to the indoor heat exchanger (41, 46).

  In the refrigerant circuit (20), one end of the liquid side communication pipe (21) is connected to the liquid side shut-off valve (36). The other end of the liquid side connecting pipe (21) is bifurcated and connected to the end of each indoor circuit (40, 45) on the indoor expansion valve (42, 47) side. On the other hand, one end of the gas side communication pipe (22) is connected to the gas side closing valve (37). The other end of the gas side connection pipe (22) is bifurcated and connected to the end of each indoor circuit (40, 45) on the indoor heat exchanger (41, 46) side. That is, in this refrigerant circuit (20), two indoor circuits (40, 45) are connected in parallel to one outdoor circuit (30).

  The compressor (31) is a hermetic compressor in which a compression mechanism and an electric motor are accommodated in one casing. Both the outdoor heat exchanger (33) and the indoor heat exchangers (41, 46) are fin-and-tube type air heat exchangers configured to exchange heat between refrigerant and air. Both the outdoor expansion valve (34) and the indoor expansion valves (42, 47) are electric expansion valves with variable opening. The four-way switching valve (32) includes a first state (state indicated by a solid line in FIG. 1) in which the first port and the third port communicate with each other, and the second port and the fourth port communicate with each other. The state is switched to a second state (state indicated by a broken line in FIG. 1) in which the port communicates with the fourth port and the second port communicates with the third port.

  The outdoor unit (11) includes a high pressure sensor (51), a low pressure sensor (52), an intake temperature sensor (53), an outdoor gas side temperature sensor (54), and an outside air temperature sensor (58). One by one. The high pressure sensor (51) is connected between the discharge side of the compressor (31) in the refrigerant circuit (20) and the first port of the four-way switching valve (32), and is discharged from the compressor (31). Measure the refrigerant pressure. The low pressure sensor (52) is connected between the suction side of the compressor (31) and the second port of the four-way switching valve (32) in the refrigerant circuit (20), and is sucked into the compressor (31). Measure the refrigerant pressure. The suction temperature sensor (53) is provided between the suction side of the compressor (31) and the second port of the four-way switching valve (32) in the refrigerant circuit (20), and is sucked into the compressor (31). Measure the temperature of the refrigerant. The outdoor gas side temperature sensor (54) is provided in the vicinity of the gas side end of the outdoor heat exchanger (33) in the outdoor circuit (30), and measures the temperature of the refrigerant passing therethrough. The outdoor air temperature sensor (58) measures the temperature of the outdoor air before passing through the outdoor heat exchanger (33).

  Each indoor unit (12, 13) is provided with one indoor temperature sensor (55a, 55b), one indoor gas side temperature sensor (56, 56b), and one indoor liquid side temperature sensor (57, 57b). Yes. The indoor temperature sensor (55a, 55b) measures the temperature of the indoor air before passing through the indoor heat exchanger (41, 46). The indoor gas side temperature sensor (56, 56b) is located near the end of each indoor circuit (40, 45) opposite to the indoor expansion valve (42, 47) of the indoor heat exchanger (41, 46). The temperature of the refrigerant | coolant which is provided and passes there is measured. The indoor liquid side temperature sensor (57, 57b) is provided in the vicinity of the end of each indoor circuit (40, 45) on the indoor expansion valve (42, 47) side of the indoor heat exchanger (41, 46), The temperature of the refrigerant passing there is measured.

  The main controller (60) is installed in the outdoor unit (11). As shown in FIG. 2, the main controller (60) includes a low pressure target value setting unit (61), a high pressure target value setting unit (62), a compressor control unit (63), and an outdoor expansion valve control unit ( 64) and a superheat degree target value changing section (65). The main controller (60) includes a high pressure sensor (51), a low pressure sensor (52), a suction temperature sensor (53), an outdoor gas side temperature sensor (54), each indoor temperature sensor (55a, 55b), and an outside The measured value of the temperature sensor (58) is input.

  One sub-controller (70a, 70b) is installed in each indoor unit (12, 13). As shown in FIG. 2, each sub-controller (70a, 70b) is provided with an indoor expansion valve controller (71a, 71b). The measured values of the low-pressure sensor (52) are input to the sub controllers (70a, 70b). In addition, each sub-controller (70a, 70b) measures the indoor gas side temperature sensor (56, 56b) and the indoor liquid side temperature sensor (57, 57b) installed in the same indoor unit (12, 13). A value is entered.

  The main controller (60) and the sub controllers (70a, 70b) control the operation of the air conditioner (10) using the measurement values input from the sensors. Details of the control operation performed by the main controller (60) and the sub-controllers (70a, 70b) will be described later.

-Air conditioner operation-
The air conditioner (10) of the present embodiment selectively performs a cooling operation that is a cooling operation and a heating operation that is a heating operation. Switching between the cooling operation and the heating operation is performed by operating the four-way switching valve (32).

<Cooling operation>
The operation of the air conditioner (10) during the cooling operation will be described. During the cooling operation, the four-way switching valve (32) is set to the first state (the state indicated by the solid line in FIG. 1). Moreover, at the time of air_conditionaing | cooling operation, an outdoor expansion valve (34) is set to full open, and the opening degree of each indoor expansion valve (42, 47) is adjusted suitably.

  In the refrigerant circuit (20), the refrigerant circulates to perform a refrigeration cycle. In the refrigerant circuit (20) during the cooling operation, the outdoor heat exchanger (33) operates as a gas cooler, and each indoor heat exchanger (41, 46) operates as an evaporator.

  Specifically, the supercritical refrigerant discharged from the compressor (31) is sent to the outdoor heat exchanger (33) through the four-way switching valve (32) and radiates heat to the outdoor air. The refrigerant flowing out of the outdoor heat exchanger (33) flows into the liquid side communication pipe (21) through the outdoor expansion valve (34) and the receiver (35), and is then distributed to each indoor circuit (40, 45). Is done.

  The refrigerant flowing into each indoor circuit (40, 45) is reduced in pressure when passing through the indoor expansion valve (42, 47) to become a gas-liquid two-phase state, and then indoors in the indoor heat exchanger (41, 46). It absorbs heat from the air and evaporates. Each indoor unit (12, 13) supplies indoor air cooled by the indoor heat exchanger (41, 46) to the room. The refrigerant that has passed through the indoor heat exchangers (41, 46) flows into the gas side connecting pipe (22) and joins, and then is sucked into the compression through the four-way switching valve (32). The compressor (31) compresses the sucked refrigerant and discharges it.

<Heating operation>
The operation of the air conditioner (10) during the heating operation will be described. During the heating operation, the four-way selector valve (32) is set to the second state (the state indicated by the broken line in FIG. 1). Further, during the heating operation, the opening degrees of the outdoor expansion valve (34) and the indoor expansion valves (42, 47) are appropriately adjusted.

  In the refrigerant circuit (20), the refrigerant circulates to perform a refrigeration cycle. In the refrigerant circuit (20) during the heating operation, each indoor heat exchanger (41, 46) operates as a gas cooler, and the outdoor heat exchanger (33) operates as an evaporator.

  Specifically, the supercritical refrigerant discharged from the compressor (31) flows into the gas side communication pipe (22) through the four-way switching valve (32), and then to each indoor circuit (40, 45). Distributed to. The refrigerant that has flowed into the indoor circuits (40, 45) radiates heat to the indoor air by the indoor heat exchanger (41, 46). Each indoor unit (12, 13) supplies indoor air heated by the indoor heat exchanger (41, 46) to the room. The refrigerant flowing out of the indoor heat exchanger (41, 46) flows into the liquid side connection pipe (21) after passing through the indoor expansion valve (42, 47), and then flows into the outdoor circuit (30).

  The refrigerant flowing into the outdoor circuit (30) is sent to the outdoor expansion valve (34) after passing through the receiver (35), and is reduced in pressure when passing through the outdoor expansion valve (34) to be in a gas-liquid two-phase state. The refrigerant that has passed through the outdoor expansion valve (34) is sent to the outdoor heat exchanger (33), and absorbs heat from the outdoor air to evaporate. The refrigerant flowing out of the outdoor heat exchanger (33) is sucked into the compressor (31) through the four-way switching valve (32). The compressor (31) compresses the sucked refrigerant and discharges it.

-Operation of main controller and sub-controller-
As described above, the main controller (60) and the sub-controllers (70a, 70b) control the operation of the air conditioner (10) using the measurement values input from the sensors.

<Cooling operation>
The operation of the main controller (60) and the sub controllers (70a, 70b) during the cooling operation will be described. During the cooling operation, the main controller (60) is operated by the low pressure target value setting unit (61), the compressor control unit (63), and the superheat degree target value changing unit (65). ), The outdoor expansion valve control section (64) performs only the operation of keeping the opening degree of the outdoor expansion valve (34) fully open, and the high pressure target value setting section (62) is stopped. Furthermore, in each sub controller (70a, 70b), each indoor expansion valve control part (71a, 71b) operates.

  The indoor expansion valve controllers (71a, 71b) of the sub controllers (70a, 70b) adjust the opening degree of the indoor expansion valves (42, 47) provided in the corresponding indoor units (12, 13). That is, in the first indoor unit (12), the indoor expansion valve control unit (71a) of the sub controller (70a) has a degree of superheat of the refrigerant at the outlet of the first indoor heat exchanger (41). The opening degree of the first indoor expansion valve (42) is adjusted so as to be the target value. In the second indoor unit (13), the indoor expansion valve control unit (71b) of the sub controller (70b) has a superheat degree of the refrigerant at the outlet of the second indoor heat exchanger (46). The opening degree of the second indoor expansion valve (47) is adjusted so as to reach the target value.

  The control operation performed by each indoor expansion valve controller (71a, 71b) will be described in detail. The indoor expansion valve control unit (71a, 71b) determines the detected value of the low pressure sensor (52) from the detected value of the indoor gas side temperature sensor (56, 56b) provided in the corresponding indoor unit (12, 13). By subtracting the saturation temperature of the refrigerant, the degree of superheat of the refrigerant at the outlet of the indoor heat exchanger (41, 46) provided in the corresponding indoor unit (12, 13) is calculated. And the opening degree of the indoor expansion valve (42, 47) provided in the corresponding indoor unit (12, 13) is adjusted so that the calculated value of the superheat degree becomes the superheat degree target value. The opening control of the indoor expansion valves (42, 47) by the indoor expansion valve control units (71a, 71b) is performed by general feedback control such as PID control.

  Specifically, the indoor expansion valve control unit (71a, 71b) increases the superheat degree of the refrigerant at the outlet of the indoor heat exchanger (41, 46) when the calculated superheat value is smaller than the superheat degree target value. In order to do so, the flow rate of the refrigerant passing through the indoor heat exchanger (41, 46) is reduced by reducing the opening of the indoor expansion valve (42, 47). Further, the indoor expansion valve control unit (71a, 71b) reduces the superheat degree of the refrigerant at the outlet of the indoor heat exchanger (41, 46) when the calculated value of the superheat degree is larger than the superheat degree target value. The flow rate of the refrigerant passing through the indoor heat exchanger (41, 46) is increased by increasing the opening of the indoor expansion valve (42, 47). In the indoor expansion valve control units (71a, 71b), the superheat degree target value is set to a constant standard value (for example, 5 ° C.) except when it is changed by the superheat degree target value changing part (65). Yes.

  The low pressure target value setting unit (61) is configured to perform a low pressure target value setting operation. In this low pressure target value setting operation, the low pressure target value, which is the low pressure target value of the refrigeration cycle, is set to a value corresponding to the cooling load in the indoor units (12, 13) during the cooling operation.

  Specifically, the low pressure target value setting unit (61) determines whether the indoor unit (12, 13) has sufficient or insufficient cooling capacity based on the measured value of each indoor temperature sensor (55a, 55b), the indoor set temperature during cooling, etc. Judging. If the low pressure target value setting unit (61) determines that the cooling capacity of the indoor units (12, 13) is insufficient, the low pressure target value setting unit (61) decreases the low pressure target value to increase the cooling capacity. Further, when the low pressure target value setting unit (61) determines that the cooling capacity in the indoor units (12, 13) is excessive, it raises the low pressure target value in order to decrease the cooling capacity.

  The compressor control unit (63) is configured to perform a capacity control operation. In this capacity control operation, the operating capacity of the compressor (31) is adjusted so that the measured value of the low pressure sensor (52) (that is, the measured value of the low pressure of the refrigeration cycle) becomes the low pressure target value. That is, the compressor control unit (63) uses the low pressure of the refrigeration cycle as a control parameter, and adjusts the operating capacity of the compressor (31) so that the control parameter becomes the low pressure target value.

  Specifically, the compressor control unit (63) changes the frequency of the alternating current supplied to the electric motor of the compressor (31) and changes the rotational speed of the compression mechanism driven by the electric motor (31). ) Is changed. When the measured value of the low pressure sensor (52) is higher than the low pressure target value, the compressor control unit (63) rotates the rotation speed of the motor of the compressor (31) to reduce the low pressure of the refrigeration cycle. To increase the operating capacity of the compressor (31). Further, when the measured value of the low pressure sensor (52) is lower than the low pressure target value, the compressor control unit (63) rotates the motor speed of the compressor (31) to increase the low pressure of the refrigeration cycle. To reduce the operating capacity of the compressor (31).

  At that time, the compressor control unit (63) uses the measured value of the low-pressure sensor (52) and a predetermined control gain to command the change amount of the AC frequency supplied to the motor of the compressor (31). Is calculated. Specifically, in the compressor control unit (63), as the difference between the measured value of the low pressure sensor (52) and the low pressure target value increases, the command value for the change amount of the AC frequency becomes larger, and the low pressure sensor (52 The smaller the difference between the measured value) and the low pressure target value, the smaller the command value for changing the AC frequency.

    In addition, the compressor control unit (63) determines that the measured value of the low pressure sensor (52) is lower than the low pressure target value even though the frequency of the alternating current supplied to the motor of the compressor (31) has reached the lower limit value. If the low state continues for a predetermined time, it is determined that the cooling capacity is excessive with respect to the cooling load, and the compressor (31) is stopped. Furthermore, the compressor control unit (63) determines that the room needs to be cooled when the difference between the measured value of the room temperature sensor (55a, 55b) and the indoor set temperature during cooling reaches a certain level. Start the compressor (31).

  The superheat degree target value changing unit (65) is configured to perform a superheat degree target value changing operation. In this superheat degree target value changing operation, the superheat degree target value changing section (65) counts the number of times the compressor (31) is stopped by the compressor control section (63). The superheat degree target value changing unit (65) sets the number of times the compressor is stopped by the compressor control unit (63) to a predetermined value (for example, twice) within a predetermined time (for example, within 15 minutes). When reaching, the superheat target value is forcibly increased from a standard value (for example, 5 ° C.). After the superheat degree target value changer (65) forcibly raises the superheat degree target value, the indoor expansion valve controller (71a, 71b) uses the superheat degree target value raised from the standard value to expand the room. Adjust the opening of the valves (42, 47).

  However, if the superheat degree of the refrigerant flowing out from the indoor heat exchanger (41, 46) becomes too high during the cooling operation, the superheat degree of the refrigerant sucked into the compressor (31) becomes too high, and the compressor (31 There is a possibility that the temperature of the refrigerant discharged from the above will become too high. For this reason, in the superheat degree target value changing unit (65), the upper limit of the superheat degree target value by the superheat degree target value changing operation is limited so that the temperature of the refrigerant discharged from the compressor (31) does not become too high. Value is set.

<Heating operation>
Operations of the main controller (60) and the sub controllers (70a, 70b) during the heating operation will be described. During the heating operation, the main controller (60) operates the high pressure target value setting unit (62), the compressor control unit (63), the outdoor expansion valve control unit (64), and the superheat degree target value changing unit (65). And the low pressure target value setting unit (61) is suspended. Furthermore, in each sub controller (70a, 70b), each indoor expansion valve control part (71a, 71b) operates.

  The indoor expansion valve controllers (71a, 71b) of the sub controllers (70a, 70b) adjust the opening degree of the indoor expansion valves (42, 47) provided in the corresponding indoor units (12, 13). This point is the same as the operation during the cooling operation. However, the indoor expansion valve control units (71a, 71b) during heating operation have the detection values of the indoor liquid side temperature sensors (57, 57b) provided in the corresponding indoor units (12, 13) as the predetermined target values. The opening degree of the indoor expansion valve (42, 47) is adjusted so as to be. That is, the indoor expansion valve control unit (71a, 71b) during the heating operation is configured so that the refrigerant temperature at the outlet of the indoor heat exchanger (41, 46) operating as a gas cooler becomes a predetermined target value. Adjust the opening of (42,47). The opening control of the indoor expansion valves (42, 47) by the indoor expansion valve control units (71a, 71b) is performed by general feedback control such as PID control.

  Specifically, when the detected value of the indoor liquid side temperature sensor (57, 57b) is higher than the target value, the indoor expansion valve control unit (71a, 71b) is arranged at the outlet of the indoor heat exchanger (41, 46). In order to reduce the temperature of the refrigerant, the flow rate of the refrigerant passing through the indoor heat exchanger (41, 46) is reduced by reducing the opening of the indoor expansion valve (42, 47). Further, the indoor expansion valve control unit (71a, 71b), when the detected value of the indoor liquid side temperature sensor (57, 57b) is lower than the target value, the refrigerant at the outlet of the indoor heat exchanger (41, 46). In order to increase the temperature, the flow rate of the refrigerant passing through the indoor heat exchanger (41, 46) is increased by increasing the opening of the indoor expansion valve (42, 47).

  The high pressure target value setting unit (62) is configured to perform a high pressure target value setting operation. In this high pressure target value setting operation, the high pressure target value, which is the high pressure target value of the refrigeration cycle, is set to a value corresponding to the heating load in the indoor units (12, 13) during the heating operation.

  Specifically, the high-pressure target value setting unit (62) determines whether the indoor unit (12, 13) is overheated or insufficient based on the measured value of each indoor temperature sensor (55a, 55b), the indoor set temperature during heating, etc. Judging. When the high pressure target value setting unit (62) determines that the heating capacity of the indoor units (12, 13) is insufficient, the high pressure target value setting unit (62) raises the high pressure target value to increase the heating capacity. Further, when the high pressure target value setting unit (62) determines that the heating capacity in the indoor units (12, 13) is excessive, it lowers the high pressure target value in order to decrease the heating capacity.

  The compressor control unit (63) is configured to perform a capacity control operation. In this capacity control operation, the operating capacity of the compressor (31) is adjusted so that the measured value of the high pressure sensor (51) (that is, the actual measured value of the high pressure of the refrigeration cycle) becomes the high pressure target value. That is, the compressor control unit (63) uses the high pressure of the refrigeration cycle as a control parameter, and adjusts the operating capacity of the compressor (31) so that the control parameter becomes the high pressure target value.

  Specifically, the compressor control unit (63) changes the frequency of the alternating current supplied to the electric motor of the compressor (31) and changes the rotational speed of the compression mechanism driven by the electric motor (31). ) Is changed. When the measured value of the high pressure sensor (51) is lower than the high pressure target value, the compressor control unit (63) rotates the motor speed of the compressor (31) to increase the high pressure of the refrigeration cycle. To increase the operating capacity of the compressor (31). Further, when the measured value of the high pressure sensor (51) is higher than the high pressure target value, the compressor control unit (63) rotates the rotational speed of the motor of the compressor (31) to reduce the high pressure of the refrigeration cycle. To reduce the operating capacity of the compressor (31).

  At that time, the compressor control unit (63) uses the measured value of the high pressure sensor (51) and a predetermined control gain to command the change amount of the AC frequency supplied to the motor of the compressor (31). Is calculated. Specifically, in the compressor control unit (63), as the difference between the measured value of the high pressure sensor (51) and the high pressure target value becomes larger, the command value for the change amount of the AC frequency becomes larger, and the high pressure sensor (51 The smaller the difference between the measured value and the high pressure target value, the smaller the command value for the change amount of the AC frequency.

  The outdoor expansion valve control unit (64) is configured to perform a flow rate control operation. In this flow control operation, the degree of opening of the outdoor expansion valve (34) is adjusted so that the superheat degree of the refrigerant at the outlet of the outdoor heat exchanger (33) that operates as an evaporator during heating operation becomes the superheat degree target value. Is done. That is, the outdoor expansion valve control unit (64) controls the flow rate of the refrigerant passing through the outdoor expansion valve (34) by adjusting the opening degree of the outdoor expansion valve (34). The opening degree control of the outdoor expansion valve (34) by the outdoor expansion valve control unit (64) is performed by general feedback control such as PID control.

  The outdoor expansion valve control unit (64) subtracts the saturation temperature of the refrigerant at the detection value of the low-pressure sensor (52) from the detection value of the outdoor gas side temperature sensor (54), so that the outdoor heat exchanger (33) The degree of superheat of the refrigerant at the outlet is calculated. And the opening degree of an outdoor expansion valve (34) is adjusted so that the calculated value of this superheat degree may become a superheat degree target value. Specifically, when the calculated value of the superheat degree is smaller than the superheat degree target value, the outdoor expansion valve control unit (64) increases the superheat degree of the refrigerant at the outlet of the outdoor heat exchanger (33). The flow rate of the refrigerant passing through the outdoor heat exchanger (33) is reduced by reducing the opening of the outdoor expansion valve (34). Further, the outdoor expansion valve control unit (64), when the calculated value of the superheat degree is larger than the target value of the superheat degree, increases the outdoor expansion in order to reduce the superheat degree of the refrigerant at the outlet of the outdoor heat exchanger (33). The flow rate of the refrigerant passing through the outdoor heat exchanger (33) is increased by increasing the opening of the valve (34).

  The superheat degree target value changing unit (65) is configured to perform a superheat degree target value changing operation. That is, as in the cooling operation, when the number of times the compressor is stopped by the compressor control unit (63) reaches a predetermined value within a predetermined time, the superheat degree target value changing unit (65) The degree target value is forcibly increased from a standard value (for example, 5 ° C.). After the superheat degree target value changing unit (65) forcibly raises the superheat degree target value, the outdoor expansion valve control part (64) uses the superheat degree target value raised from the standard value to set the outdoor expansion valve ( Adjust the opening in 34).

  However, if the superheat degree of the refrigerant flowing out of the outdoor heat exchanger (33) becomes too high during the heating operation, the superheat degree of the refrigerant sucked into the compressor (31) becomes too high, and the refrigerant (31) There is a possibility that the temperature of the discharged refrigerant becomes too high. For this reason, in the superheat degree target value changing unit (65), the upper limit of the superheat degree target value by the superheat degree target value changing operation is limited so that the temperature of the refrigerant discharged from the compressor (31) does not become too high. Value is set.

-Effect of Embodiment 1-
In this embodiment, the superheat target value changing unit (65) of the main controller (60) has an excessive capacity of the air conditioner (10), and the compressor control unit (63) stops the compressor (31). When the frequency increases, the superheat target value is forcibly increased from the standard value. During the cooling operation, the indoor expansion valve controller (71a, 71b) of the sub controller (70a, 70b) causes the degree of superheat of the refrigerant from the indoor heat exchanger (41, 46) to the compressor (31). The opening degree of the indoor expansion valve (42, 47) is adjusted so that the raised superheat degree target value is obtained. During heating operation, the outdoor expansion valve control unit (64) of the main controller (60) is used to increase the superheat degree of the refrigerant from the outdoor heat exchanger (33) to the compressor (31). The opening degree of the outdoor expansion valve (34) is adjusted so as to be a value.

  Here, assuming that the temperature and flow rate of air sent to the evaporator are constant, the degree of superheat of the refrigerant at the outlet of the evaporator increases as the flow rate of the refrigerant passing through the evaporator decreases. Therefore, the opening degree of the indoor expansion valves (42, 47) and the outdoor expansion valve (34) decreases as the superheat degree target value increases. That is, the indoor expansion valves (42, 47) and the outdoor expansion valve (34) are in a state where the flow rate of the refrigerant passing therethrough is reduced (that is, the opening degree is set to be small). For this reason, compared with the case where the rotational speed of the compression mechanism provided in the compressor (31) is the same, the higher the superheat degree target value, the smaller the amount of refrigerant circulating in the refrigerant circuit (20). As a result, the air conditioner (10) ability is reduced.

  That is, the higher the superheat degree target value, the lower the lower limit value of the capacity of the air conditioner (10). For this reason, even if the compressor control unit (63) had to stop the compressor (31) before raising the target superheat, the operation of the compressor (31) was increased after raising the target superheat. Is likely to continue.

  Thus, according to this embodiment, in the air conditioner (10) that performs a so-called supercritical cycle, the compressor (31) is caused by the capacity of the air conditioner (10) being excessive with respect to the load. Can be reduced. In other words, capacity adjustment in the air conditioner (10) that performs the supercritical cycle with the characteristic that “the power required for the high pressure and low pressure of the refrigeration cycle to reach appropriate values after starting the compressor (31) increases” Therefore, the number of times the compressor (31) starts and stops can be reduced. Therefore, according to the present embodiment, the power consumed during the operation of the air conditioner (10) can be reduced by reducing the number of times the compressor (31) is started and stopped for capacity adjustment. ) Driving efficiency can be improved.

<< Embodiment 2 of the Invention >>
A second embodiment of the present invention will be described. The present embodiment is obtained by changing the configuration of the main controller (60) in the air conditioner (10) of the first embodiment.

  As shown in FIG. 3, the main controller (60) of the present embodiment is provided with a control target value changing unit (66) instead of the superheat degree target value changing unit (65) of the first embodiment. . In the main controller (60) of the present embodiment, the operations of the low pressure target value setting unit (61), the high pressure target value setting unit (62), the compressor control unit (63), and the outdoor expansion valve control unit (64) Is the same as the operation in the first embodiment.

  The control target value changing unit (66) is configured to perform a control target value changing operation. In this control target value changing operation, the control target value changing unit (66) counts the number of times the compressor (31) has been stopped by the compressor control unit (63). Then, the control target value changing unit (66) reaches the predetermined value (for example, twice) within a predetermined time (for example, within 15 minutes) the number of times the compressor has been stopped by the compressor control unit (63). Then, the control target value used in the compressor control unit (63) is forcibly changed.

<Operation during cooling operation>
During the cooling operation, the control target value changing unit (66) performs an operation for forcibly changing the low pressure target value as a control target value changing operation. Specifically, when the number of times the compressor is stopped by the compressor control unit (63) reaches a predetermined number within a predetermined time, the control target value changing unit (66) causes the compressor control unit (63) to The low pressure target value to be used is raised from the standard target value which is the value determined by the low pressure target value setting unit (61). Then, when the compressor (31) is subsequently started, the compressor control unit (63) uses the low-pressure target value raised by the control target value changing unit (66), and the compressor (31) Adjust the operating capacity. Further, the compressor control unit (63) sets the value of the low pressure target value so that the low pressure target value becomes the standard target value when a predetermined time (for example, 4 minutes) has elapsed since the start of the compressor (31). Pull it down gradually.

  Here, immediately after the compressor (31) is started, the difference between the measured value of the low-pressure sensor (52) and the standard target value is large. For this reason, if the low pressure target value remains the standard target value immediately after the compressor (31) is started, the compressor (31) is used to bring the measured value of the low pressure sensor (52) close to the standard target value as soon as possible. ) Is rapidly increased. And if the cooling capacity of the air conditioner (10) suddenly increases with the sudden increase in capacity of the compressor (31), the room temperature will be reduced within a relatively short time after the compressor (31) is started. The temperature becomes lower than the set temperature, and the compressor (31) must be stopped again.

  On the other hand, the control target value changing unit (66) of the present embodiment sets the low pressure target value to a value higher than the standard target value for a while after the compressor (31) is started. Accordingly, even immediately after the compressor (31) is started, the difference between the measured value of the low pressure sensor (52) and the low pressure target value is smaller than when the low pressure target value remains the standard target value. . As a result, the rapid capacity increase of the compressor (31) after the start of the compressor (31) is suppressed, and the cooling capacity of the air conditioner (10) also changes gradually. Therefore, if the control target value changing unit (66) makes the low pressure target value higher than the standard target value as in the present embodiment, the compressor control unit (63) compresses if the low pressure target value remains the standard target value. Even in a situation where the machine (31) has to be stopped, the possibility that the operation of the compressor (31) can be continued increases.

<Operation during heating operation>
During the heating operation, the control target value changing unit (66) performs an operation for forcibly changing the high pressure target value as a control target value changing operation. Specifically, when the number of times the compressor is stopped by the compressor control unit (63) reaches a predetermined number within a predetermined time, the control target value changing unit (66) causes the compressor control unit (63) to The high-pressure target value to be used is lowered from the standard target value that is a value determined by the high-pressure target value setting unit (62). Then, when the compressor (31) is subsequently started, the compressor control unit (63) uses the high-pressure target value lowered by the control target value changing unit (66), so that the compressor (31) Adjust the operating capacity. Further, the compressor control unit (63) sets the value of the high pressure target value so that the high pressure target value becomes the standard target value when a predetermined time (for example, 4 minutes) has elapsed since the start of the compressor (31). Pull it up gradually.

  Here, immediately after the compressor (31) is started, the difference between the measured value of the high-pressure sensor (51) and the standard target value is large. For this reason, if the high pressure target value remains the standard target value immediately after the compressor (31) is started, the compressor (31) is used to bring the measured value of the high pressure sensor (51) close to the standard target value as soon as possible. ) Is rapidly increased. And if the heating capacity of the air conditioner (10) increases suddenly with the sudden increase in capacity of the compressor (31), the room temperature will be reduced in a relatively short time after the compressor (31) is started. The temperature exceeds the set temperature, and the compressor (31) must be stopped again.

  On the other hand, the control target value changing unit (66) of the present embodiment sets the high pressure target value to a value lower than the standard target value for a while after the compressor (31) is started. Accordingly, even immediately after the compressor (31) is started, the difference between the measured value of the high pressure sensor (51) and the high pressure target value is smaller than when the high pressure target value remains the standard target value. . As a result, the rapid capacity increase of the compressor (31) after the start of the compressor (31) is suppressed, and the heating capacity of the air conditioner (10) also changes gradually. For this reason, if the control target value changing unit (66) makes the high pressure target value lower than the standard target value as in this embodiment, the compressor control unit (63) compresses if the high pressure target value remains the standard target value. Even in a situation where the machine (31) has to be stopped, the possibility that the operation of the compressor (31) can be continued increases.

-Effect of Embodiment 2-
According to this embodiment, in the air conditioner (10) performing a so-called supercritical cycle, the compressor (31) can be stopped due to the capacity of the air conditioner (10) being excessive with respect to the load. Can be reduced. Therefore, according to the present embodiment, as in the first embodiment, the power consumed during the operation of the air conditioner (10) is reduced by reducing the number of times the compressor (31) is started and stopped for capacity adjustment. The operating efficiency of the air conditioner (10) can be improved.

-Modification of Embodiment 2-
The compressor control unit (63) of the present embodiment may be configured to use the evaporation temperature of the refrigerant in the indoor heat exchanger (41, 46) operating as an evaporator as a control parameter during cooling operation. . In the main controller (60) of this modification, an evaporation temperature target value setting unit is provided instead of the low pressure target value setting unit (61). The evaporating temperature target value setting unit sets a target value of the evaporating temperature of the refrigerant in the indoor heat exchanger (41, 46) according to the cooling load of the air conditioner (10). In addition, the control target value changing unit (66) of the present modified example uses the evaporation temperature target value setting unit to set the evaporation temperature target value used in the compressor control unit (63) as the control target value changing operation during the cooling operation. The evaporating temperature target value is gradually increased so that the evaporating temperature target value becomes the standard target value when a predetermined time has elapsed from the start of the compressor (31) while being raised from the standard target value which is the determined value. I will pull it down.

<< Embodiment 3 of the Invention >>
Embodiment 3 of the present invention will be described. The present embodiment is obtained by changing the configuration of the main controller (60) in the air conditioner (10) of the first embodiment.

  As shown in FIG. 4, the main controller (60) of the present embodiment is provided with a gain adjusting unit (67) instead of the superheat degree target value changing unit (65) of the first embodiment. In the main controller (60) of the present embodiment, the operations of the low pressure target value setting unit (61), the high pressure target value setting unit (62), the compressor control unit (63), and the outdoor expansion valve control unit (64) Is the same as the operation in the first embodiment.

  The gain adjustment unit (67) is configured to perform a gain adjustment operation. In this gain adjustment operation, the gain adjustment unit (67) is configured to change the compressor control unit (63) according to the difference between the measured value of the outside air temperature sensor (58) (that is, the actually measured value of the outside air temperature) and the indoor set temperature. ) Is adjusted.

  During the cooling operation, the gain adjuster (67) compares the measured value of the outside air temperature sensor (58) with the indoor set temperature. During the cooling operation, the cooling load in the room decreases as the value obtained by subtracting the set temperature in the room from the measured value of the outside air temperature sensor (58) decreases. Therefore, the gain adjuster (67) sets the control gain used in the compressor controller (63) to a smaller value as the value obtained by subtracting the indoor set temperature from the measured value of the outside air temperature sensor (58) becomes smaller. .

  During the cooling operation, the compressor control unit (63) of the present embodiment adjusts the capacity of the compressor (31) using a small control gain set by the gain adjustment unit (67). Specifically, the compressor control unit (63) uses the difference between the measured value of the low pressure sensor (52), the low pressure target value, and the control gain to determine the frequency of the alternating current supplied to the motor of the compressor (31). The command value for the amount of change is calculated. When the difference between the measured value of the low-pressure pressure sensor (52) and the low-pressure target value is the same, in the compressor control unit (63), the command value for the change amount of the AC frequency decreases as the control gain value decreases. .

  Even during the heating operation, the gain adjuster (67) compares the measured value of the outside air temperature sensor (58) with the set temperature in the room. During the heating operation, the indoor heating load decreases as the value obtained by subtracting the measured value of the outside air temperature sensor (58) from the indoor set temperature decreases. Therefore, the gain adjustment unit (67) sets the control gain used in the compressor control unit (63) to a smaller value as the value obtained by subtracting the measured value of the outside air temperature sensor (58) from the indoor set temperature becomes smaller. .

  During the heating operation, the compressor control unit (63) of the present embodiment adjusts the capacity of the compressor (31) using a small control gain set by the gain adjustment unit (67). Specifically, the compressor control unit (63) uses the difference between the measured value of the high pressure sensor (51), the high pressure target value, and the control gain to determine the frequency of the alternating current supplied to the motor of the compressor (31). The command value for the amount of change is calculated. When the difference between the measured value of the high pressure sensor (51) and the high pressure target value is the same, in the compressor control unit (63), the command value for the change amount of the AC frequency decreases as the control gain value decreases. .

  Here, if the control gain used in the compressor control unit (63) remains large despite the load on the air conditioner (10) being small, the measured value of the low pressure sensor (52) and the low pressure target value Or the command value for the change amount of the AC frequency determined based on the difference between the measured value of the high pressure sensor (51) and the high pressure target value. As a result, the capacity of the air conditioner (10) becomes excessive with respect to the load, and there is a high possibility that the compressor (31) must be stopped.

  On the other hand, the gain adjustment unit (67) of the present embodiment decreases the value of the control gain as the load on the air conditioner (10) decreases. As a result, the command value calculated using the measured value of the low pressure sensor (52) or the high pressure sensor (51) and the control gain is smaller than when the control gain is constant. Therefore, when the gain adjustment unit (67) reduces the control gain as in this embodiment, the compressor control unit (63) has to stop the compressor (31) if the control gain remains constant. Even in the situation, there is a high possibility that the operation of the compressor (31) can be continued.

-Effect of Embodiment 3-
According to this embodiment, in the air conditioner (10) performing a so-called supercritical cycle, the compressor (31) can be stopped due to the capacity of the air conditioner (10) being excessive with respect to the load. Can be reduced. Therefore, according to the present embodiment, as in the first embodiment, the power consumed during the operation of the air conditioner (10) is reduced by reducing the number of times the compressor (31) is started and stopped for capacity adjustment. The operating efficiency of the air conditioner (10) can be improved.

<< Other Embodiments >>
The refrigerant circuit (20) of the air conditioner (10) of each of the above embodiments is provided with an expander composed of a rotary fluid machine, a scroll fluid machine, or the like instead of the outdoor expansion valve (34). Also good. In the refrigerant circuit (20) of the present modification, this expander constitutes an expansion mechanism.

  The main controller (60) of the present modification is provided with an expander control unit instead of the outdoor expansion valve control unit (64). The expander control unit is configured to perform a flow rate control operation in the same manner as the outdoor expansion valve control unit (64). In this flow control operation, the rotational speed of the expander is adjusted so that the superheat degree of the refrigerant at the outlet of the outdoor heat exchanger (33) operating as an evaporator during the heating operation becomes the superheat degree target value. That is, the expander control unit controls the flow rate of the refrigerant passing through the expander by adjusting the rotation speed of the expander. The rotation speed control of the expander by the expander control unit is performed by general feedback control such as PID control.

  Specifically, when the calculated superheat value is smaller than the target superheat value, the expander control unit rotates the expander to increase the superheat degree of the refrigerant at the outlet of the outdoor heat exchanger (33). Reduce speed. When the rotation speed of the expander decreases, the flow rate of the refrigerant passing through the expander decreases and the flow rate of the refrigerant passing through the outdoor heat exchanger (33) also decreases. In addition, when the calculated value of the superheat degree is larger than the superheat degree target value, the expander control unit sets the rotation speed of the expander in order to reduce the superheat degree of the refrigerant at the outlet of the outdoor heat exchanger (33). Raise. When the rotational speed of the expander increases, the flow rate of the refrigerant passing through the expander increases and the flow rate of the refrigerant passing through the outdoor heat exchanger (33) also increases.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or its use.

  As described above, the present invention is useful for a refrigeration apparatus that performs a refrigeration cycle in which the high pressure is set to a value higher than the critical pressure of the refrigerant.

It is a refrigerant circuit figure which shows schematic structure of the air conditioner of Embodiment 1. FIG. 2 is a block diagram illustrating configurations of a main controller and a sub controller according to the first embodiment. FIG. 6 is a block diagram illustrating a configuration of a main controller according to a second embodiment. It is a block diagram which shows the structure of the main controller of Embodiment 3.

Explanation of symbols

10 Air conditioner (refrigeration equipment)
20 Refrigerant circuit
31 Compressor
33 Outdoor heat exchanger (heat source side heat exchanger)
34 Outdoor expansion valve (expansion mechanism)
41 Indoor heat exchanger (use side heat exchanger)
42 Indoor expansion valve (expansion mechanism)
46 Indoor heat exchanger (use side heat exchanger)
47 Indoor expansion valve (expansion mechanism)
60 Main controller
70a Sub controller
70b Sub controller
80 Control means

Claims (4)

The compressor (31), expansion mechanism (34, 42, 47), heat source side heat exchanger (33), and use side heat exchanger (41, 46) are connected, and the high pressure is higher than the critical pressure of the refrigerant. A refrigerant circuit (20) for performing a refrigeration cycle set to
A refrigeration apparatus comprising control means (80) for controlling the compressor (31) and the expansion mechanism (34, 42, 47),
The control means (80)
A capacity control operation for adjusting the capacity of the compressor (31) so that the physical quantity indicating the operation state of the refrigeration cycle performed in the refrigerant circuit (20) becomes a control target value;
Of the heat source side heat exchanger (33) and the use side heat exchanger (41, 46), the degree of superheat of the refrigerant from the one operating as an evaporator toward the compressor (31) becomes the superheat degree target value. And a flow rate control operation for adjusting the flow rate of the refrigerant passing through the expansion mechanism (34, 42, 47),
When the compressor (31) is stopped by the capacity control operation, a superheat degree target value changing operation for forcibly raising the superheat degree target value is performed. apparatus. The compressor (31), expansion mechanism (34, 42, 47), heat source side heat exchanger (33), and use side heat exchanger (41, 46) are connected, and the high pressure is higher than the critical pressure of the refrigerant. A refrigerant circuit (20) for performing a refrigeration cycle set to
Control means (80) for controlling the compressor (31),
The refrigeration apparatus performs at least a cooling operation in which the heat source side heat exchanger (33) operates as a gas cooler and the use side heat exchanger (41, 46) operates as an evaporator,
The control means (80)
The compressor evaporating temperature of the refrigerant in the use side heat exchanger (41, 46) or the low pressure of the refrigeration cycle performed in the refrigerant circuit (20) is a control parameter, and the compressor is set so that the control parameter becomes a control target value. A capacity control operation for adjusting the capacity of (31);
A control target value for gradually decreasing the control target value after starting the compressor (31) so that the control target value becomes a predetermined standard target value after a predetermined time has elapsed since the start of the compressor (31). A refrigeration apparatus configured to perform a changing operation. The compressor (31), expansion mechanism (34, 42, 47), heat source side heat exchanger (33), and use side heat exchanger (41, 46) are connected, and the high pressure is higher than the critical pressure of the refrigerant. A refrigerant circuit (20) for performing a refrigeration cycle set to
Control means (80) for controlling the compressor (31),
A refrigeration apparatus that performs at least a heating operation in which the use side heat exchanger (41, 46) operates as a gas cooler and the heat source side heat exchanger (33) operates as an evaporator,
The control means (80)
A capacity control operation in which the high pressure of the refrigeration cycle performed in the refrigerant circuit (20) is a control parameter, and the capacity of the compressor (31) is adjusted so that the control parameter becomes a control target value;
A control target value for gradually increasing the control target value after starting the compressor (31) so that the control target value becomes a predetermined standard target value after a predetermined time has elapsed since the start of the compressor (31). A refrigeration apparatus configured to perform a changing operation. The compressor (31), expansion mechanism (34, 42, 47), heat source side heat exchanger (33), and use side heat exchanger (41, 46) are connected, and the high pressure is higher than the critical pressure of the refrigerant. A refrigerant circuit (20) for performing a refrigeration cycle set to
A refrigeration apparatus comprising control means (80) for controlling the compressor (31),
The control means (80)
The capacity of the compressor (31) based on the command value calculated using the physical quantity and the control gain so that the physical quantity indicating the operating state of the refrigeration cycle performed in the refrigerant circuit (20) becomes the control target value. Capacity control operation to adjust,
A refrigeration apparatus configured to perform a gain adjustment operation for decreasing the control gain as the load of the refrigeration apparatus decreases.

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