JP2014016096A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner that eliminates a deficiency in heating capacity by reducing stagnation of a liquid refrigerant in a liquid pipe.SOLUTION: When recognizing that a refrigerant stagnates in a liquid pipe, CPUs 110a, 110b make opening degrees of first outdoor expansion valves 40a, 40b and second outdoor expansion valves 41a, 41b larger by a predetermined change amount or more. The predetermined change amount indicates a predetermined rate at which the opening degrees of the first outdoor expansion valves 40a, 40b and second outdoor expansion valves 41, 41b are increased at certain intervals, and when the number of pulses supplied to the first outdoor expansion valves 40a, 40b and second outdoor expansion valves 41, 41b is increased by two or more under opening degree control corresponding to a found refrigerant overheating degree, the first outdoor expansion valves 40a, 40b and second outdoor expansion valves 41, 41b are made larger in opening degree Vo.

Description

  The present invention relates to an air conditioner in which at least one outdoor unit and a plurality of indoor units are connected by a plurality of refrigerant pipes, and more particularly to an air conditioner that eliminates the retention of refrigerant in the refrigerant pipes. .

  Conventionally, as an air conditioner in which a plurality of indoor units are connected in parallel to a plurality of refrigerant pipes to at least one outdoor unit, a multi-type air conditioner that can simultaneously perform cooling operation or heating operation in all indoor units, There is known an air conditioner capable of performing a so-called cooling / heating-free operation that can be performed by selecting a cooling operation and a heating operation for each machine.

  For example, an air conditioner described in Patent Literature 1 includes a compressor, an accumulator, an oil separator, a receiver tank, two outdoor heat exchangers, and an outdoor expansion valve connected to each outdoor heat exchanger. , One outdoor unit provided with a discharge valve and a suction valve, two indoor units each provided with an indoor heat exchanger, and two electromagnetic valves connected to each indoor heat exchanger. And two solenoid valve units that switch between the discharge side (high pressure side) and the suction side (low pressure side).

  These outdoor units, indoor units, and solenoid valve units are connected by refrigerant piping as follows. The discharge pipe connected to the discharge side of the compressor is branched after connecting to the oil separator, one branch pipe is connected to the outdoor heat exchanger via the discharge valve, and the other branch pipe is connected to each solenoid valve unit. Connected to the indoor heat exchanger. These discharge pipes and branch pipes constitute a high-pressure gas pipe.

  Also, the suction pipe connected to the suction side of the compressor is branched after being connected to the accumulator, one branch pipe is connected to the outdoor heat exchanger via the suction valve, and the other branch pipe is connected to each solenoid valve unit. To the indoor heat exchanger. These suction pipes and branch pipes constitute a low-pressure gas pipe.

  Furthermore, one end of the refrigerant pipe is branched and connected to the connection port on the side opposite to the connection port to which the discharge valve and the suction valve in the outdoor heat exchanger are connected. The other end of the pipe branches after being connected to the receiver tank, and each branch pipe is connected to a connection port opposite to the connection port to which the electromagnetic valve unit in each indoor heat exchanger is connected. These refrigerant pipes and branch pipes constitute a liquid pipe.

  In the air conditioner described above, each indoor heat exchanger is individually switched by switching the indoor heat exchanger to be connected to the discharge side or suction side of the compressor by opening and closing each solenoid valve of the solenoid valve unit. It can function as a condenser or an evaporator, and can perform cooling operation and heating operation simultaneously in each indoor unit.

JP 2004-286253 A (pages 6-7, FIG. 1)

  In the above-described air conditioner, when all (two) indoor units perform the heating operation, or when one unit performs the heating operation and the rest performs the cooling operation, it is required for the indoor unit that performs the heating operation. When the capacity is higher than the capacity required for the indoor unit performing the cooling operation (hereinafter referred to as heating main operation), various valves are controlled to open and close so that the outdoor heat exchanger functions as an evaporator.

  When performing a heating operation or a heating main operation, the opening degree of the outdoor expansion valve corresponding to the outdoor heat exchanger functioning as an evaporator is controlled by, for example, the degree of refrigerant superheat at the refrigerant outlet of the outdoor heat exchanger. Has been made. The refrigerant superheat degree can be obtained by subtracting the low-pressure saturation temperature calculated using the pressure of the refrigerant flowing through the low-pressure gas pipe (hereinafter referred to as low pressure) from the refrigerant temperature at the refrigerant outlet of the outdoor heat exchanger.

  Specifically, the opening degree control of the outdoor expansion valve is performed so that the refrigerant superheat degree becomes a predetermined target refrigerant superheat degree. When the refrigerant heating degree calculated with respect to the target refrigerant superheat degree is small, the low pressure is lowered by reducing the opening amount of the outdoor expansion valve and reducing the amount of refrigerant flowing to the outdoor heat exchanger. As a result, the low pressure saturation temperature is lowered and the refrigerant temperature at the refrigerant outlet of the outdoor heat exchanger is raised, so that the degree of refrigerant superheat increases. Moreover, when the refrigerant | coolant heating degree calculated with respect to the target refrigerant | coolant superheat degree is large, the low pressure is raised by increasing the opening degree of an outdoor expansion valve and increasing the refrigerant | coolant amount which flows into an outdoor heat exchanger. As a result, the low-pressure saturation temperature rises and the refrigerant temperature at the refrigerant outlet of the outdoor heat exchanger decreases, so that the degree of refrigerant superheat decreases.

  By the way, when the outside air temperature is high (for example, 10 ° C. or higher) when the air conditioner performs the heating operation or the heating main operation, the pressure of the refrigerant flowing through the high-pressure gas pipe (hereinafter referred to as high pressure) becomes high. As a result, the upper limit of the discharge pressure allowed in the compressor may be exceeded. In such a case, for example, a hot gas bypass pipe provided so as to communicate the high pressure gas pipe and the low pressure gas pipe, or an oil separator provided on the discharge side of the compressor and the low pressure gas pipe are communicated. The high pressure is lowered by reducing the high pressure using the oil return pipe provided in the compressor or by reducing the rotational speed of the compressor.

  On the other hand, when the high pressure is lowered using a hot gas bypass pipe or an oil return pipe, or when the high pressure is lowered by lowering the rotational speed of the compressor, the low pressure rises accordingly. If the low pressure rises, the low pressure saturation temperature also rises, so the refrigerant heating degree calculated using the low pressure saturation temperature becomes small. In this case, as described above, in order to make the refrigerant superheat degree close to the target refrigerant superheat degree, control is performed so that the degree of refrigerant superheat becomes large by reducing the opening degree of the outdoor expansion valve. However, if the high pressure continues for a long time (for example, 10 minutes or more) and the control for reducing the high pressure using a hot gas bypass pipe or the like becomes a long time, the low pressure continues for a long time. Therefore, the state where the opening degree of the outdoor expansion valve is small continues for a long time.

  If the opening degree of the outdoor expansion valve is reduced, the indoor heat of the indoor unit that is performing the heating operation is connected to the liquid pipe that connects the indoor heat exchanger of the indoor unit that is performing the heating operation and the outdoor expansion valve of the outdoor unit. Gas-liquid two-phase refrigerant that has exchanged heat with room air in the exchanger (functioning as a condenser) stays in the liquid pipe, but stays in the liquid pipe if the outdoor expansion valve is kept open for a long time. As the amount of refrigerant increases, the refrigerant pressure in the liquid pipe rises and the gas-liquid two-phase refrigerant that stays condenses to become liquid refrigerant. When the liquid pipe is filled with the liquid refrigerant, the liquid refrigerant is accumulated in the indoor heat exchanger, and there is a problem that the condensation capacity in the indoor heat exchanger is reduced and the heating capacity is insufficient.

  The present invention solves the above-described problems, and an object of the present invention is to provide an air conditioner that solves the shortage of heating capacity by reducing the retention of liquid refrigerant in the liquid pipe.

  In order to solve the above-described problems, an air conditioner according to the present invention includes a compressor, an outdoor heat exchanger, and a refrigerant discharge port or a refrigerant suction port of the compressor connected to one refrigerant inlet / outlet of the outdoor heat exchanger. A flow path switching means for switching the connection of the outdoor heat exchanger to the flow path, a flow rate adjusting means for adjusting a refrigerant flow rate in the outdoor heat exchanger connected to the other refrigerant inlet / outlet of the outdoor heat exchanger, a flow path switching means, A plurality of outdoor units having control means for controlling the flow rate adjusting means, and a plurality of indoor units connected to the outdoor unit by one liquid pipe and at least one gas pipe. The flow rate adjusting means and the indoor heat exchanger are connected by a liquid pipe, and the outdoor heat exchanger functions as an evaporator on the flow rate adjusting means side in the liquid pipe. Outdoor unit side refrigerant temperature detection means on the refrigerant inflow side of the outdoor heat exchanger The indoor unit-side refrigerant temperature detecting means is provided on the refrigerant outflow side of the indoor heat exchanger when the indoor heat exchanger functions as a condenser, on the indoor heat exchanger side of the liquid pipe. Is. Then, the control means controls the flow path switching means to cause the outdoor heat exchanger to function as an evaporator, and the outdoor unit side refrigerant temperature and the indoor unit side refrigerant temperature taken in from the outdoor unit side refrigerant temperature detection means. If the temperature difference from the indoor unit side refrigerant temperature taken in from the detection means is within a predetermined value, the opening degree of the flow rate adjustment means is increased by a predetermined change amount.

  According to the air conditioner of the present invention configured as described above, the outdoor heat exchanger functions as an evaporator, that is, when the outdoor unit side refrigerant temperature detected during the heating operation or the heating main operation is performed. By comparing the indoor unit side refrigerant temperature with the liquid pipe, it is determined whether or not the liquid refrigerant is staying in the liquid pipe, and if it is determined that the liquid refrigerant is staying in the liquid pipe, the flow rate adjustment provided in the liquid pipe By increasing the opening degree of the means by a predetermined change amount, the liquid refrigerant staying in the liquid pipe can flow to the outdoor heat exchanger side. Thereby, it can prevent that a condensation capacity falls by an indoor heat exchanger by filling a liquid refrigerant with a liquid pipe, and can suppress the shortage of the heating capacity in the indoor unit which is performing heating operation.

It is a refrigerant circuit diagram of the air conditioning apparatus which is an Example of this invention, and is a refrigerant circuit diagram explaining the flow of the refrigerant | coolant in the case of performing heating operation. It is a flowchart explaining the process in a control means in the other Example of this invention.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. As an embodiment, there is provided an air conditioner in which five indoor units are connected in parallel to two outdoor units and can be operated by selecting a cooling operation and a heating operation for each indoor unit. An example will be described. The present invention is not limited to the following embodiments, and can be variously modified without departing from the gist of the present invention.

  As shown in FIG. 1, the air conditioner 1 in this embodiment includes two outdoor units 2a and 2b, five indoor units 8a to 8e, five switching units 6a to 6e, and a branching unit 70. , 71, 72. The outdoor units 2a and 2b, the indoor units 8a to 8e, the switching units 6a to 6e, the branching units 70, 71 and 72, the high pressure gas pipe 30, the high pressure gas branch pipes 30a and 30b, the low pressure gas pipe 31, and the low pressure The refrigerant circuit of the air conditioner 1 is comprised by mutually connecting with the gas distribution pipes 31a and 31b, the liquid pipe 32, and the liquid distribution pipes 32a and 32b. The high pressure gas pipe 30 and the high pressure gas distribution pipes 30a and 30b, and the low pressure gas pipe 31 and the low pressure gas distribution pipes 31a and 31b constitute the gas pipe of the present invention, and the liquid pipe 32 and the liquid distribution pipes 32a and 32b of the present invention. The liquid pipe is constructed.

  In the air conditioner 1, according to the open / closed state of various valves provided in the outdoor units 2a and 2b and the switching units 6a to 6e, heating operation (all indoor units are heating operation), heating main operation (heating operation is performed). If the overall capacity required for the indoor unit being used exceeds the overall capacity required for the indoor unit performing cooling operation), cooling operation (all indoor units are cooling operation), cooling-main operation (cooling operation Various operation operations are possible, such as when the entire capacity required for the indoor unit being performed exceeds the total capacity required for the indoor unit performing the heating operation. In the following description, the case where the heating operation is performed from among these operation operations will be described as an example and described with reference to FIG.

  FIG. 1 is a refrigerant circuit diagram when all the indoor units 8a to 8e are performing the heating operation. First, the outdoor units 2a and 2b will be described. Since the configurations of the outdoor units 2a and 2b are all the same, only the configuration of the outdoor unit 2a will be described in the following description, and a detailed description of the outdoor unit 2b will not be given. Omitted.

  As shown in FIG. 1, the outdoor unit 2a includes a compressor 21a, a first three-way valve 22a and a second three-way valve 23a that are flow path switching means, a first outdoor heat exchanger 24a, and a second outdoor heat exchange. 25a, outdoor fan 26a, accumulator 27a, oil separator 28a, receiver tank 29a, first outdoor expansion valve 40a connected to the first outdoor heat exchanger 24a, and second outdoor heat exchanger 25a. The connected second outdoor expansion valve 41a, the hot gas bypass pipe 36a, the first electromagnetic valve 42a provided in the hot gas bypass pipe 36a, the oil return pipe 37a, and the second provided in the oil return pipe 37a. An electromagnetic valve 43a and closing valves 44a to 46a are provided. The first outdoor expansion valve 40a and the second outdoor expansion valve 41a are the flow rate adjusting means in the present invention.

  The compressor 21a is a variable capacity compressor that can vary the operating capacity by being driven by a motor (not shown) whose rotation speed is controlled by an inverter. As shown in FIG. 1, the discharge side of the compressor 21a is connected to the inflow side of the oil separator 28a by a refrigerant pipe, and the outflow side of the oil separator 28a is connected to the closing valve 44a by an outdoor unit high-pressure gas pipe 33a. ing. The suction side of the compressor 21a is connected to the outflow side of the accumulator 27a by a refrigerant pipe, and the inflow side of the accumulator 27a is connected to the closing valve 45a by an outdoor unit low-pressure gas pipe 34a.

  The first three-way valve 22a and the second three-way valve 23a are valves for switching the flow direction of the refrigerant. The first three-way valve 22a has three ports a, b, and c, and the second three-way valve 23a has d, Each of the three ports e and f is provided. In the first three-way valve 22a, the refrigerant pipe connected to the port a is connected to the outdoor unit high-pressure gas pipe 33a at the connection point A. The port b and the first outdoor heat exchanger 24a are connected by a refrigerant pipe, and the refrigerant pipe connected to the port c is connected to the outdoor unit low-pressure gas pipe 34a at a connection point D.

  In the second three-way valve 23, the refrigerant pipe connected to the port d is connected at the connection point A to the refrigerant pipe connected to the outdoor unit high-pressure gas pipe 33a and the port a of the first three-way valve 22a. Further, the port e and the second outdoor heat exchanger 25a are connected by a refrigerant pipe, and the refrigerant pipe connected to the port f is connected to the refrigerant pipe connected to the port c of the first three-way valve 22a at the connection point C. Yes.

  The 1st outdoor heat exchanger 24a and the 2nd outdoor heat exchanger 25a are comprised by many fins (not shown) formed with the aluminum material, and several copper pipes (not shown) which distribute | circulate a refrigerant | coolant inside. As described above, one refrigerant inlet / outlet of the first outdoor heat exchanger 24a is connected to the port b of the first three-way valve 22a, and the other refrigerant inlet / outlet is connected to one port of the first outdoor expansion valve 40a via the refrigerant pipe. It is connected. The other port of the first outdoor expansion valve 40a is connected to the closing valve 46a and the outdoor unit liquid pipe 35a.

  As described above, one refrigerant inlet / outlet of the second outdoor heat exchanger 25a is connected to the port e of the second three-way valve 23a via the refrigerant pipe, and the other refrigerant inlet / outlet is connected to the second outdoor expansion valve 41a via the refrigerant pipe. Is connected to one of the ports. The other port of the second outdoor expansion valve 41a is connected to a connection point B in the outdoor unit liquid pipe 35a by a refrigerant pipe.

  The first outdoor expansion valve 40a and the second outdoor expansion valve 41a are electric expansion valves that are driven by a pulse motor (not shown), and each opening degree is adjusted by the number of pulses applied to the pulse motor.

  The outdoor fan 26a is a propeller fan formed of a resin material disposed in the vicinity of the first outdoor heat exchanger 24a and the second outdoor heat exchanger 25a, and is rotated by a fan motor (not shown), so that the outdoor unit 2a The outside air is taken in and exchanged heat with the refrigerant in the first outdoor heat exchanger 24a and the second outdoor heat exchanger 25a, and then the heat-exchanged outdoor air is released to the outside of the outdoor unit 2a.

  The accumulator 27a has an inflow side connected to the outdoor unit low-pressure gas pipe 34a, and an outflow side connected to the suction side of the compressor 21a through a refrigerant pipe. The accumulator 27a separates the inflowing refrigerant into a gas refrigerant and a liquid refrigerant, and causes only the gas refrigerant to be sucked into the compressor 21a.

  The oil separator 28a has an inflow side connected to the discharge side of the compressor 21a by a refrigerant pipe, and an outflow side connected to the outdoor unit high-pressure gas pipe 33a. The oil separator 28a separates the refrigerating machine oil of the compressor 21a included in the refrigerant discharged from the compressor 21a from the refrigerant. The separated refrigerating machine oil is sucked into the compressor 21a through an oil return pipe 37a described later.

  The receiver tank 29a is provided between the connection point B in the outdoor unit liquid pipe 35a and the closing valve 46a, and is a container capable of storing a refrigerant. The receiver tank 29a is provided in the receiver tank 29a for performing gas-liquid separation of the refrigerant, which serves as a buffer for adjusting the amount of refrigerant in the first outdoor heat exchanger 24a and the second outdoor heat exchanger 25a. It has a function of removing moisture and foreign matters in the refrigerant with a filter that does not.

  One end of the hot gas bypass pipe 36a is connected to the outdoor unit high-pressure gas pipe 33a at a connection point E, and the other end is connected to the outdoor unit low-pressure gas pipe 34a at a connection point F. The hot gas bypass pipe 36a is provided with a first electromagnetic valve 42a. By opening and closing the first electromagnetic valve 42a, the hot gas bypass pipe 36a can be in a state where the refrigerant flows or does not flow.

  One end of the oil return pipe 37a is connected to the oil return port of the oil separator 28a, and the other end is connected to a refrigerant pipe connecting the suction side of the compressor 21a and the outflow side of the accumulator 27a at a connection point G. The oil return pipe 37a is provided with a second electromagnetic valve 43a. By opening and closing the second electromagnetic valve 43a, the oil return pipe 37a can be in a state where the refrigerant flows or does not flow.

  In addition to the configuration described above, the outdoor unit 2a is provided with various sensors. As shown in FIG. 1, a refrigerant pipe connecting the discharge side of the compressor 21a and the oil separator 28a is discharged from the compressor 21a and a high-pressure sensor 50a that detects the pressure of the refrigerant discharged from the compressor 21a. And a discharge temperature sensor 53a which is a discharge temperature detecting means for detecting the temperature of the refrigerant. Between the connection point F in the outdoor unit low-pressure gas pipe 34a and the inflow side of the accumulator 27a, a low-pressure sensor 51a for detecting the pressure of the refrigerant sucked into the compressor 21a and the refrigerant sucked into the compressor 21a An inhalation temperature sensor 54a for detecting the temperature is provided. Further, between the connection point B in the outdoor unit liquid pipe 32a and the closing valve 46a, an intermediate pressure sensor 52a for detecting the pressure of the refrigerant flowing through the outdoor unit liquid pipe 35a and the temperature of the refrigerant flowing through the outdoor unit liquid pipe 35a. The refrigerant temperature sensor 55a which is the outdoor unit side refrigerant temperature detection means which detects this is provided.

  The refrigerant pipe connecting the port b of the first three-way valve 22a and the first outdoor heat exchanger 24a detects the temperature of the refrigerant flowing out of the first outdoor heat exchanger 24a or flowing into the first outdoor heat exchanger 24a. A first heat exchange temperature sensor 56a is provided. Further, the refrigerant pipe connecting the port e of the second three-way valve 23a and the second outdoor heat exchanger 25a has a temperature of the refrigerant flowing out from the second outdoor heat exchanger 25a or flowing into the second outdoor heat exchanger 25a. A second heat exchange temperature sensor 57a is provided for detecting. Furthermore, an outdoor air temperature sensor 58a for detecting the temperature of the outside air flowing into the outdoor unit 2a, that is, the outside air temperature, is provided in the vicinity of a suction port (not shown) of the outdoor unit 2a.

  The outdoor unit 2a is provided with a control means 100a. The control unit 100a is mounted on a control board (not shown) and includes a CPU 110a, a storage unit 120a, and a communication unit 130a. CPU110a takes in the detection signal from each sensor mentioned above of outdoor unit 2a, and takes in the control signal output from each indoor unit 8a-8e via communication part 130a. The CPU 110a controls the drive control of the compressor 21a, the switching control of the first three-way valve 22a and the second three-way valve 23a, the rotation control of the fan motor 29a, the first outdoor expansion valve 40a and the first based on the acquired detection signal and control signal. Various controls such as the opening degree control of the two outdoor expansion valves 41a are performed.

  The storage unit 120a is composed of a ROM and a RAM, and stores detection values corresponding to control programs for the outdoor unit 2a and detection signals from each sensor. The communication unit 130a is an interface that performs communication between the outdoor unit 2a and the indoor units 8a to 8e.

  The configuration of the outdoor unit 2b is the same as that of the outdoor unit 2a, and the number assigned to the components (devices and members) of the outdoor unit 2a is changed from a to b. It becomes a component of the corresponding outdoor unit 2b. However, the symbols for the connection points of the first three-way valve, the second three-way valve, and the refrigerant pipe are different between the outdoor unit 2a and the outdoor unit 2b, and the port a in the first three-way valve 22a of the outdoor unit 2a. , B, c are ports g, h, j in the first three-way valve 22b of the outdoor unit 2b, and those corresponding to ports d, e, f in the second three-way valve 23a of the outdoor unit 2a are the outdoor units. In the 2b second three-way valve 23b, ports k, m, and n are set. In the outdoor unit 2b, the connection points H, J, K, M, N, P, and Q correspond to the connection points A, B, C, D, E, F, and G in the outdoor unit 2a.

  As shown in FIG. 1, in the refrigerant circuit during the heating operation, each three-way valve is switched so that the two outdoor heat exchangers provided in each of the outdoor units 2a and 2b function as evaporators. Specifically, in the outdoor unit 2a, the first three-way valve 22a is switched to communicate the port b and the port c, and the second three-way valve 23a is switched to communicate the port e and the port f. In the outdoor unit 2b, the first three-way valve 22b is switched so as to communicate between the port h and the port j, and the second three-way valve 23b is switched so as to communicate between the port m and the port n. In FIG. 1, the ports that communicate with the three-way valves are indicated by solid lines, and the ports that do not communicate are indicated by broken lines.

  The five indoor units 8a to 8e include indoor heat exchangers 81a to 81e, indoor expansion valves 82a to 82e, and indoor fans 83a to 83e. In addition, since the structure of all the indoor units 8a-8e is the same, in the following description, only the structure of the indoor unit 8a is demonstrated, and description is abbreviate | omitted about the other indoor units 8b-8e.

  One end of the indoor heat exchanger 81a is connected to one port of the indoor expansion valve 82a via a refrigerant pipe, and the other end is connected to a switching unit 6a described later via a refrigerant pipe. The indoor heat exchanger 81a functions as an evaporator when the indoor unit 8a performs a cooling operation, and functions as a condenser when the indoor unit 8a performs a heating operation.

  The indoor expansion valve 82 a has one port connected to the indoor heat exchanger 81 a as described above, and the other port connected to the liquid pipe 32. When the indoor heat exchanger 81a functions as an evaporator, the indoor expansion valve 82a is adjusted according to the required cooling capacity, and when the indoor heat exchanger 81a functions as a condenser, The opening is adjusted according to the required heating capacity.

  The indoor fan 83a is rotated by a fan motor (not shown), thereby taking in indoor air into the indoor unit 8a, heat-exchanging the refrigerant and indoor air in the indoor heat exchanger 81a, and then transferring the heat-exchanged air indoors. Supply.

  In addition to the configuration described above, the indoor unit 8a is provided with various sensors. The refrigerant pipe on the indoor expansion valve 82a side of the indoor heat exchanger 81a is provided with a refrigerant temperature sensor 84a, which is an indoor unit side refrigerant temperature detecting means for detecting the temperature of the refrigerant, and on the switching unit 6a side of the indoor heat exchanger 81a. Each refrigerant pipe is provided with a refrigerant temperature sensor 85a for detecting the temperature of the refrigerant. Further, a room temperature sensor 86a for detecting the temperature of the indoor air flowing into the indoor unit 8a, that is, the room temperature is provided in the vicinity of the indoor air suction port (not shown) of the indoor unit 8a.

  The configurations of the indoor units 8b to 8e are the same as those of the indoor unit 8a, and the numbers given to the constituent elements (devices and members) of the indoor unit 8a are changed from a to b, c, d, and e, respectively. However, it becomes a component of the indoor units 8b-8e corresponding to the component of the outdoor unit 8a.

  The air conditioner 1 includes five switching units 6a to 6e corresponding to the five indoor units 8a to 8e. The switching units 6a to 6e include solenoid valves 61a to 61e, solenoid valves 62a to 62e, first branch pipes 63a to 63e, and second branch pipes 64a to 64e. In addition, since all the structures of switching unit 6a-6e are the same, in the following description, only the structure of switching unit 6a is demonstrated and description is abbreviate | omitted about the other switching units 6b-6e.

  One end of the first branch pipe 63 a is connected to the high pressure gas pipe 30, and one end of the second branch pipe 64 a is connected to the low pressure gas pipe 31. Further, the other end of the first diversion pipe 63a and the other end of the second diversion pipe 64a are connected to each other, and the connection portion and the indoor heat exchanger 81a are connected by a refrigerant pipe. The first diverter pipe 63a is provided with an electromagnetic valve 61a, and the second diverter pipe 64a is provided with an electromagnetic valve 62a. By opening and closing the electromagnetic valve 61a and the electromagnetic valve 62a, the switching unit 6a is provided. The refrigerant flow path in the refrigerant circuit is switched so that the indoor heat exchanger 81a of the corresponding indoor unit 8a is connected to the discharge side (high-pressure gas pipe 30 side) or the suction side (low-pressure gas pipe 31 side) of the compressor 21. be able to.

  Note that the configuration of the switching units 6b to 6e is the same as that of the switching unit 6a as described above, and the end of the numbers given to the components (devices and members) of the switching unit 6a are a to b, c, d and e. Those changed to the above are the constituent elements of the switching units 6b to 6e corresponding to the constituent elements of the switching unit 6a.

  The outdoor units 2a and 2b, the indoor units 8a to 8e and the switching units 6a to 6e described above, the high pressure gas pipe 30, the high pressure gas distribution pipes 30a and 30b, the low pressure gas pipe 31, the low pressure gas distribution pipes 31a and 31b, the liquid pipe 32, The connection state with the liquid distribution pipes 32a and 32b and the branching devices 70, 71, and 72 will be described with reference to FIG. One end of the high-pressure gas branch pipes 30a and 30b is connected to the shut-off valves 44a and 44b of the outdoor units 2a and 2b, respectively, and the other end of the high-pressure gas branch pipes 30a and 30b is connected to the branch device 70, respectively. One end of the high-pressure gas pipe 30 is connected to the branching device 70, and the other end of the high-pressure gas pipe 30 is branched and connected to the first branch pipes 63a to 63e of the switching units 6a to 6e.

  One ends of the low-pressure gas distribution pipes 31a and 31b are connected to the shut-off valves 45a and 45b of the outdoor units 2a and 2b, respectively, and the other ends of the low-pressure gas distribution pipes 31a and 31b are connected to the branch device 71, respectively. One end of the low-pressure gas pipe 31 is connected to the branching device 71, and the other end of the low-pressure gas pipe 31 is branched and connected to the second branch pipes 64a to 64e of the switching units 6a to 6e.

  One ends of the liquid distribution pipes 32a and 32b are connected to the closing valves 46a and 46b of the outdoor units 2a and 2b, respectively, and the other ends of the liquid distribution pipes 32a and 32b are connected to the branching device 72, respectively. One end of the liquid pipe 32 is connected to the branching device 72, and the other end of the liquid pipe 32 is branched and connected to refrigerant pipes connected to the indoor expansion valves 82a to 82e of the indoor units 8a to 8e, respectively.

The connection points of the indoor heat exchangers 81a to 81e of the corresponding indoor units 8a to 8e and the first branch pipes 63a to 63e and the second branch pipes 64a to 64e in the switching units 6a to 6e are refrigerant pipes, respectively. Connected.
With the connection described above, the refrigerant circuit of the air conditioner 1 is configured, and the refrigeration cycle is established by flowing the refrigerant through the refrigerant circuit.

  Next, the operation | movement operation | movement of the air conditioning apparatus 1 in a present Example is demonstrated using FIG. In addition, in FIG. 1, when each heat exchanger with which the outdoor units 2a and 2b and indoor unit 8a-8e were equipped becomes a condenser, hatching is attached | subjected, and when it becomes an evaporator, it illustrates in white. Further, the first electromagnetic valves 42a and 42b and the second electromagnetic valves 43a and 43b provided in the outdoor units 2a and 2b, and the electromagnetic valves 61a to 61e and the electromagnetic valves 62a to 62e provided in the switching units 6a to 6e are opened and closed. As for the state, the closed state is illustrated in black, and the open state is illustrated in white. Moreover, the arrow has shown the flow of the refrigerant | coolant.

  As shown in FIG. 1, when all the indoor units 8a to 8e perform the heating operation, and the heating capacity required by these is high and it is necessary to operate all the outdoor units 2a and 2b, in the outdoor unit 2a, The port b and the port c of the first three-way valve 22a are switched so as to communicate with each other, the first outdoor heat exchanger 24a functions as an evaporator, and the port e and the port f of the second three-way valve 23a are switched to communicate with each other. Thus, the second outdoor heat exchanger 25a functions as an evaporator. In the outdoor unit 2b, the port h and the port j of the first three-way valve 22b are switched so as to communicate with each other, and the first outdoor heat exchanger 24b functions as an evaporator, and the port m and the port of the second three-way valve 23b. The second outdoor heat exchanger 25b functions as an evaporator by switching so as to communicate with n. The first electromagnetic valves 42a and 42b and the second electromagnetic valves 43a and 43b of the outdoor units 2a and 2b are both closed, and the hot gas bypass pipes 36a and 36b and the oil return pipes 37a and 37b are both refrigerant and Refrigerating machine oil is not allowed to flow.

  In the indoor units 8a to 8e, the electromagnetic valves 61a to 61e of the switching units 6a to 6e corresponding to the respective indoor units 8a to 8e are opened so that the refrigerant flows through the first branch pipes 63a to 63e, and the electromagnetic valves 62a to 62e are closed to The refrigerant is prevented from flowing through the two branch pipes 64a to 64e. Thereby, all the indoor heat exchangers 81a to 81e of the indoor units 8a to 8e function as a condenser.

  The high-pressure refrigerant discharged from the compressors 21a and 21b flows through the outdoor unit high-pressure gas pipes 33a and 33b via the oil separators 28a and 28b, and flows into the high-pressure gas branch pipes 30a and 30b via the shut-off valves 44a and 44b. . The high-pressure refrigerant that has flowed into the high-pressure gas branch pipes 30a and 30b joins at the branching device 70, flows through the high-pressure gas pipe 30, and flows into the switching units 6a to 6e from the high-pressure gas pipe 30.

  The high-pressure refrigerant that has flowed into the switching units 6a to 6e flows through the first branch pipes 63a to 63e provided with the open electromagnetic valves 61a to 61e, and flows out of the switching units 6a to 6e. Flows into the indoor units 8a to 8e corresponding to 6e.

  The high-pressure refrigerant flowing into the indoor units 8a to 8e flows into the indoor heat exchangers 81a to 81e, exchanges heat with the indoor air, and condenses. Thereby, room air is warmed and the room in which indoor unit 8a-8e was installed is heated. The high-pressure refrigerant that has flowed out of the indoor heat exchangers 81a to 81e passes through the indoor expansion valves 82a to 82e and is depressurized. The opening degree of the indoor expansion valves 82a to 82e is determined in accordance with the degree of supercooling of the refrigerant at the refrigerant outlet of the indoor heat exchangers 81a to 81e. The degree of supercooling of the refrigerant is determined, for example, from a high-pressure saturation temperature (corresponding to the condensation temperature in the indoor heat exchangers 81a to 81e) calculated from the pressure detected by the high-pressure sensors 50a and 50b of the outdoor units 2a and 2b. It is obtained by subtracting the refrigerant temperature (the indoor unit side refrigerant temperature Tif described later) at the refrigerant outlet of the indoor heat exchangers 81a to 81e detected by 84a to 84e.

  The intermediate-pressure refrigerant that has flowed out of the indoor units 8a to 8e flows into the liquid pipe 32, joins in the liquid pipe 32, and flows into the branching device 72. The intermediate-pressure refrigerant branched from the branching device 72 to the liquid distribution pipes 32a and 32b flows into the outdoor units 2a and 2b via the closing valves 46a and 46b. The intermediate-pressure refrigerant that has flowed into the outdoor units 2a and 2b flows through the outdoor unit liquid pipes 35a and 35b, and is divided at the connection points B and J to be divided into the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b. The refrigerant is reduced in pressure through a low pressure refrigerant.

  The opening degree of the first outdoor expansion valves 40a, 40b is determined according to the degree of superheat of the refrigerant at the refrigerant outlet of the first outdoor heat exchangers 24a, 24b. The opening degree of the second outdoor expansion valves 41a and 41b is determined according to the degree of superheat of the refrigerant at the refrigerant outlet of the second outdoor heat exchangers 25a and 25b. The degree of superheat of the refrigerant is, for example, that of the first outdoor heat exchangers 24a and 24b and the second outdoor heat exchangers 25a and 25b detected by the first heat exchange temperature sensors 56a and 56b and the second heat exchange temperature sensors 57a and 57b. Low pressure saturation temperature calculated from the pressure detected by the low pressure sensors 51a and 51b of the outdoor units 2a and 2b from the refrigerant temperature at the refrigerant outlet (inside the first outdoor heat exchangers 24a and 24b and in the second outdoor heat exchangers 25a and 25b) Is equivalent to the evaporation temperature of

  Note that the CPUs 110a and 110b of the control means 100a and 100b have the degree of superheat of the refrigerant at the refrigerant outlet of the first outdoor heat exchangers 24a and 24b and the second outdoor heat exchangers 25a and 25a at predetermined timing (for example, every 30 seconds). The degree of superheat of the refrigerant at the refrigerant outlet 25b is obtained, and the opening degree of the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b is controlled accordingly.

  The low-pressure refrigerant depressurized by the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b flows into the first outdoor heat exchangers 24a and 24b and the second outdoor heat exchangers 25a and 25b, and the outside air Evaporate with heat exchange. The low-pressure refrigerant flowing out of the first outdoor heat exchangers 24a and 24b and the second outdoor heat exchangers 25a and 25b is connected to the connection point C via the first three-way valves 22a and 22b and the second three-way valves 23a and 23b. , K, and flows into the outdoor unit low-pressure gas pipes 34a, 34b at the connection points D, M. The low-pressure refrigerant flowing into the outdoor unit low-pressure gas pipes 34a and 34b is sucked into the compressors 21a and 21b via the connection points F and P and the accumulators 27a and 27b, and is compressed again.

  Next, with reference to FIG. 1 and FIG. 2, the operation of the refrigerant circuit according to the present invention and the operation and effect thereof in the air-conditioning apparatus 1 of the present embodiment will be described. First, the liquid pipe 32 and liquid distribution pipes 32a and 32b and the outdoor unit liquid pipes 35a and 35b between the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b and the indoor heat exchangers 81a to 81e ( Hereinafter, the refrigerant circuit operation when the refrigerant stays in the liquid pipe), and the refrigerant temperature detected by the refrigerant temperature sensors 55a and 55b, unless otherwise mentioned, are collectively referred to as a liquid pipe) The reason why it is possible to determine whether or not the refrigerant is staying in the liquid pipe by comparing the refrigerant temperatures detected by the refrigerant temperature sensors 84a to 84e will be described.

  When the air conditioner 1 is performing heating operation in the refrigerant circuit as shown in FIG. 1, the CPUs 110 a and 110 b are the first outdoor heat exchangers 24 a and 24 b and the second outdoor heat exchangers that function as evaporators. The first outdoor expansion valves 40a and 40b and the second outdoor heat exchangers 41a and 41b are set so that the refrigerant superheat degree at the refrigerant outlets 25a and 25b becomes the target refrigerant superheat degree stored in the storage units 120a and 120b in advance. The degree of opening is controlled.

  When the outside air temperature is high (for example, 10 ° C. or more) during the heating operation as described above, the high pressure, that is, the discharge pressure detected by the high pressure sensors 50a and 50b becomes high, and the compressors 21a and 21b. May exceed the upper limit of the discharge pressure allowed. In such a case, for example, the CPUs 110a and 110b open the first electromagnetic valves 42a and 42b and the second electromagnetic valves 43a and 43b, and set the hot gas bypass pipes 36a and 36b and the oil return pipes 37a and 37b as refrigerant or refrigerator oil. In order to reduce the high pressure, control is performed.

  If the refrigerant or refrigerating machine oil flows through the hot gas bypass pipes 36a and 36b and the oil return pipes 37a and 37b, the high pressure decreases and the low pressure increases. If the low pressure rises, the low pressure saturation temperature also rises. Therefore, the refrigerant superheat degree at the refrigerant outlet of the first outdoor heat exchangers 24a, 24b and the second outdoor heat exchangers 25a, 25b becomes small and becomes smaller than the target refrigerant superheat degree. .

  At this time, the CPUs 110a and 110b reduce the opening degree of the first outdoor expansion valves 40a and 40b and the second outdoor heat exchangers 41a and 41b in order to increase the refrigerant superheat degree to the target refrigerant superheat degree. As a result, the amount of refrigerant flowing through the first outdoor heat exchangers 24a, 24b and the second outdoor heat exchangers 25a, 25b decreases, so the low pressure decreases and the low pressure saturation temperature also decreases. Further, the amount of refrigerant flowing through the first outdoor heat exchangers 24a and 24b and the second outdoor heat exchangers 25a and 25b is reduced, so that the first outdoor heat exchangers 24a and 24b and the second outdoor heat exchangers 25a and 25b are reduced. The refrigerant temperature at the refrigerant outlet (the refrigerant temperature detected by the first heat exchange temperature sensors 56a and 56b and the second heat exchange temperature sensors 57a and 57b) rises. Therefore, the refrigerant superheat degree can be increased and increased to the target refrigerant superheat degree.

  As described above, if the opening degree of the first outdoor expansion valves 40a and 40b and the second outdoor heat exchangers 41a and 41b is reduced, the liquid heat pipe is condensed by the indoor heat exchangers 81a to 81e and the indoor heat exchanger 81a. The refrigerant in the gas-liquid two-phase state that has flowed out from ~ 81e stays. The state in which the refrigerant or refrigerating machine oil flows through the hot gas bypass pipes 36a, 36b and the oil return pipes 37a, 37b continues for a long time (for example, 10 minutes or more), and the first outdoor expansion valves 40a, 40b and the second If the outdoor heat exchangers 41a and 41b are kept in a small state, the refrigerant pressure in the liquid pipe rises and the gas-liquid two-phase refrigerant that stays condenses into liquid refrigerant.

  If the opening degree of the first outdoor expansion valves 40a and 40b and the second outdoor heat exchangers 41a and 41b continues to be small, the liquid pipe is filled with liquid refrigerant, and the liquid refrigerant stays in the indoor heat exchangers 81a to 81e. As a result, the condensing capacity in the indoor heat exchangers 81a to 81e is lowered and the heating capacity is insufficient. At this time, since the liquid pipe is filled with the liquid refrigerant, the refrigerant temperature detected by the refrigerant temperature sensors 84a to 84e (hereinafter referred to as indoor unit side refrigerant temperature Tif) and the refrigerant temperature detected by the refrigerant temperature sensors 55a and 55b. The temperature difference Δt with respect to the outdoor unit side refrigerant temperature Toe (hereinafter referred to as the outdoor unit side refrigerant temperature Toe) becomes zero. Therefore, by comparing the indoor unit side refrigerant temperature Tif and the outdoor unit side refrigerant temperature Toe (see the difference temperature Δt), it can be determined whether or not the liquid refrigerant is retained in the liquid pipe.

  Next, using FIG. 1 and FIG. 2, it is determined whether or not the refrigerant is retained in the liquid pipe, and the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b are determined according to the determination result. A method for controlling the opening will be specifically described. The flowchart shown in FIG. 2 shows the flow of processing when the opening degree control of the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b is performed. ST represents a step and is a number that follows this step. Represents a step number. Note that FIG. 2 mainly describes the processing related to the present invention, and other general processing such as control of the refrigerant circuit corresponding to the operating conditions such as the set temperature and the air volume instructed by the user will be described. Is omitted.

  First, the CPUs 110a and 110b fetch the operation mode and the operation capability requested by the user in the indoor units 8a to 8e from the indoor units 8a to 8e via the communication units 130a and 130b, and perform the heating operation or the heating main operation. (ST1).

  When performing the heating operation or the heating main operation (ST1-Yes), the CPU 110a, 110b switches the first three-way valve 22a, 22b or the second three-way valve 23a, 23b of each outdoor unit 2a, 2b to perform the heating operation or Perform heating-based operation.

  Specifically, the CPU 110a switches the first three-way valve 22a so that the port b and the port c communicate with each other, and switches the second three-way valve 23a so that the port e and the port f communicate with each other (see FIG. 1). State shown by solid line). Thereby, the 1st outdoor heat exchanger 24a and the 2nd outdoor heat exchanger 25a function as an evaporator. Then, the CPU 110a drives the compressor 21a at a rotational speed corresponding to the required operating capacity, and the opening degree of the first outdoor expansion valve 40a is determined according to the refrigerant superheat degree at the refrigerant outlet of the first outdoor heat exchanger 24a. The opening degree of the second outdoor expansion valve 41a is set to an opening degree corresponding to the degree of refrigerant superheat at the refrigerant outlet of the second outdoor heat exchanger 25a.

  Similarly, the CPU 110b switches the first three-way valve 22b so that the port h and the port j communicate with each other, and switches the second three-way valve 23b so that the port m and the port n communicate with each other (shown by a solid line in FIG. 1). State shown). Thereby, the 1st outdoor heat exchanger 24b and the 2nd outdoor heat exchanger 25b function as an evaporator. Then, the CPU 110b drives the compressor 21b at a rotational speed corresponding to the required driving capability, and the opening degree of the first outdoor expansion valve 40b is determined according to the refrigerant superheat degree at the refrigerant outlet of the first outdoor heat exchanger 24b. The opening degree of the second outdoor expansion valve 41b is set to an opening degree corresponding to the degree of refrigerant superheating at the refrigerant outlet of the second outdoor heat exchanger 25b.

  The CPUs 110a and 110b perform the heating operation or the heating main operation by controlling the outdoor units 2a and 2b as described above. The refrigerant superheat degree is, for example, the low pressure saturation temperature calculated using the pressure detected by the low pressure sensors 51a and 51b and the refrigerant detected by the first heat exchange temperature sensors 56a and 56b and the second heat exchange temperature sensors 57a and 57b. The CPU 110a, 110b can determine the refrigerant superheat degree periodically (for example, every 30 seconds. Compared with the change time of the low pressure saturation temperature due to the change in low pressure, the first outdoor heat exchanger 24a, 24b and the second outdoor heat exchangers 25a and 25b take a long time to change the temperature of the refrigerant, which is a relatively long time interval), and the first outdoor expansion valve 40a according to the obtained refrigerant superheat degree, The opening degree of 40b and the 2nd outdoor expansion valves 41a and 41b is determined.

  The CPUs 110a and 110b take in the outdoor unit side refrigerant temperature Toe detected by the refrigerant temperature sensors 55a and 55b and perform the indoor unit side refrigerant temperature Tif detected by the refrigerant temperature sensors 84a to 84e during the heating operation described above. Are taken in from the indoor units 8a to 8e via the communication units 130a and 130b (ST2).

  Next, the CPUs 110a and 110b determine whether or not the refrigerant stagnation generation condition is satisfied (ST3). Here, the refrigerant stagnation generation condition is whether or not the difference temperature Δt between the taken outdoor unit side refrigerant temperature Toe and the indoor unit side refrigerant temperature Tif is equal to or lower than a predetermined temperature (for example, 6 ° C.). If the temperature Δt is 6 ° C. or less, it is a condition that the liquid refrigerant may be retained in the liquid pipe. Note that the CPUs 110a and 110b periodically perform the processing from ST2 to ST3 (for example, every 5 seconds).

  When the refrigerant stagnation generation condition is satisfied (ST3-Yes), the CPUs 110a and 110b transmit a refrigerant stagnation elimination control start signal to other outdoor units (ST4), and the process proceeds to ST5. Here, the refrigerant stagnation elimination control start signal instructs other outdoor units to perform refrigerant stagnation elimination control described later. For example, when the refrigerant stagnation generation condition is satisfied in the outdoor unit 2a, The CPU 110a transmits a refrigerant retention elimination control start signal to the outdoor unit 2b.

  On the other hand, when the refrigerant stagnation generation condition is not satisfied (ST3-No), the CPUs 110a and 110b determine whether or not a refrigerant stagnation elimination control start signal has been received from another outdoor unit (ST9). For example, when the refrigerant stagnation generation condition is satisfied in the outdoor unit 2a described above, the CPU 110b determines whether or not the refrigerant stagnation elimination control start signal is received from the outdoor unit 2a.

  If the stay elimination control start signal is not received (ST9-No), the CPU 110b controls the opening degree of the normal first outdoor expansion valve 40b and the second outdoor expansion valve 41b (the first outdoor heat exchanger 24b and the second outdoor heat exchanger 24b). (Opening degree control according to the degree of refrigerant superheating at the refrigerant outlet of the outdoor heat exchanger 25b) is performed (ST13), and the process returns to ST1. If the stay cancellation control start signal has been received (ST9-Yes), the CPUs 110a and 110b advance the process to ST5.

  In ST5, the CPUs 110a and 110b execute the refrigerant stagnation elimination control by increasing the opening degree of the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b by a predetermined change amount or more (ST5). Here, the predetermined amount of change refers to the degree of opening of the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b, and the first outdoor heat exchanger 24a, 24b and the second outdoor heat exchangers 25a and 25b, and flows into the compressors 21a and 21b, indicating that the so-called liquid back does not occur and increases at a predetermined rate, for example, 30 seconds. Every time, the number of pulses given to the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b is increased by two pulses.

  In the above-described refrigerant retention elimination control, the ratio of increasing the opening degree of the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b is set to the predetermined change amount “more than” for the following reason. . The CPUs 110a and 110b also perform control based on the degree of refrigerant superheat of the opening degrees of the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b in combination with the refrigerant retention elimination control. . Therefore, when the number of pulses applied to the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b is increased by two or more by opening control according to the obtained refrigerant superheat degree, the first outdoor The opening degree of the expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b is increased.

  Further, when the number of pulses applied to the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b is increased by one pulse or the number of pulses is decreased by opening control according to the obtained refrigerant superheat degree, Since the elimination of the liquid refrigerant retention in the pipe is delayed or the liquid refrigerant residence proceeds, the number of pulses given to the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b with priority given to the refrigerant residence elimination control as described above. Is increased by 2 pulses every 30 seconds.

  In the above description, the opening change amount of the first outdoor expansion valves 40a, 40b and the second outdoor expansion valves 41a, 41b is determined by the opening change amount determined according to the refrigerant superheat degree and the refrigerant stagnation elimination control. Although the case where it determines by comparing with the variation | change_quantity of this was demonstrated, the compressor which detected the opening amount variation | change_quantity of 1st outdoor expansion valve 40a, 40b and 2nd outdoor expansion valve 41a, 41b with discharge temperature sensor 53a, 53b Similarly, when it is determined according to the discharge temperatures of 21a and 21b, it is determined by comparison with a predetermined change amount by the refrigerant stagnation elimination control.

  Specifically, when the discharge temperature detected by the discharge temperature sensors 53a and 53b exceeds the upper limit value of the discharge temperature determined by the compressors 21a and 21b, the CPUs 110a and 110b, the first outdoor expansion valves 40a and 40b. And the discharge temperature is controlled to decrease by increasing the opening of the second outdoor expansion valves 41a and 41b and increasing the amount of refrigerant sucked into the compressors 21a and 21b.

  Therefore, when the number of pulses applied to the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b is increased by two pulses or more by opening degree control according to the detected discharge temperature, the first outdoor expansion is performed accordingly. The opening degree of the valves 40a and 40b and the second outdoor expansion valves 41a and 41b is increased. When the number of pulses applied to the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b is increased by one pulse or the number of pulses is decreased by opening control according to the detected discharge temperature, Since the liquid refrigerant stagnation is delayed or the liquid refrigerant stagnation proceeds, the priority is given to the refrigerant stagnation control, and the number of pulses given to the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b is set every 30 seconds. Increase by 2 pulses.

  As described above, by controlling the opening degree of the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b, the liquid refrigerant staying in the liquid pipes is allowed to flow into the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 40a and 40b. It passes through the two outdoor expansion valves 41a and 41b, flows to the first outdoor heat exchangers 24a and 24b and the second indoor heat exchangers 25a and 25b, and passes through the first three-way valves 22a and 22b and the second three-way valves 23a and 23b. Into the accumulators 27a and 27b. Thereby, the liquid refrigerant stagnation in the liquid pipe is eliminated.

  Next, the CPUs 110a and 110b determine whether or not the refrigerant retention elimination condition is satisfied (ST6). Here, the refrigerant retention elimination condition is whether or not the difference temperature Δt between the taken outdoor unit side refrigerant temperature Toe and the indoor unit side refrigerant temperature Tif is greater than a predetermined temperature (for example, 6 ° C.). If Δt is greater than 6 ° C., it is a condition that liquid refrigerant stagnation in the liquid pipe is considered to be eliminated. If the refrigerant retention cancellation condition is not satisfied (ST6-No), the CPUs 110a and 110b return the process to ST1, and if the refrigerant retention cancellation condition is satisfied (ST6-Yes), the CPUs 110a and 110b The cancellation control is stopped (ST7), and the process proceeds to ST8.

  In ST8, the CPUs 110a and 110b determine whether or not it is necessary to end the operation of the outdoor units 2a and 2b by stopping the operation of all the indoor units 8a to 8e. If it is necessary to end the operation (ST8-Yes), the CPUs 110a and 110b stop the compressors 21a and 21b and fully close the first outdoor expansion valves 40a and 40b and the second outdoor expansion valves 41a and 41b. The process is terminated. If it is not necessary to end the operation (ST8-No), the CPUs 110a and 110b return the process to ST1.

  In ST1, when the heating operation or the heating main operation is not performed (ST1-No), the CPUs 110a and 110b determine whether or not the refrigerant stagnation elimination control is being executed (ST10). This determination is, for example, a determination necessary when switching from the state where the heating operation or the heating main operation is performed to the cooling operation or the cooling main operation. When the refrigerant retention elimination control is not being executed (ST10-No), the CPUs 110a and 110b advance the process to ST12. When the refrigerant stagnation elimination control is being executed (ST10-Yes), the CPUs 110a and 110b stop the refrigerant stagnation elimination control (ST11) and advance the process to ST12.

  In ST12, the CPUs 110a and 110b perform the cooling operation or the cooling main operation by switching the first three-way valves 22a and 22b and the second three-way valves 23a and 23b of the outdoor units 2a and 2b. Specifically, the CPU 110a switches the first three-way valve 22a so that the port a and the port b communicate with each other, and switches the second three-way valve 23a so that the port d and the port e communicate with each other (see FIG. 1). State indicated by a broken line). Thereby, the 1st outdoor heat exchanger 24a and the 2nd outdoor heat exchanger 25a function as a condenser. Then, the CPU 110a drives the compressor 21a at a rotation speed corresponding to the required operating capacity, and fully opens the opening of the first outdoor expansion valve 40a or refrigerant supercooling at the refrigerant outlet of the first outdoor heat exchanger 24a. The opening of the second outdoor expansion valve 41a is fully opened or the opening according to the degree of refrigerant supercooling at the refrigerant outlet of the second outdoor heat exchanger 25a.

  Similarly, the CPU 110b switches the first three-way valve 22b so that the port g and the port h communicate with each other, and switches the second three-way valve 23b so that the port k and the port m communicate with each other (as indicated by a broken line in FIG. 1). State shown). Thereby, the 1st outdoor heat exchanger 24b and the 2nd outdoor heat exchanger 25b function as a condenser. Then, the CPU 110b drives the compressor 21b at a rotational speed corresponding to the required operating capacity, and fully opens the opening of the first outdoor expansion valve 40b or refrigerant supercooling at the refrigerant outlet of the first outdoor heat exchanger 24b. The opening degree of the second outdoor expansion valve 41b is fully opened or the opening degree according to the degree of refrigerant supercooling at the refrigerant outlet of the second outdoor heat exchanger 25b.

  The CPUs 110a and 110b control the outdoor units 2a and 2b as described above to execute the cooling operation or the cooling main operation, and return the process to ST1. Note that the refrigerant supercooling degree can be obtained by using, for example, the high pressure saturation temperature calculated using the pressure detected by the high pressure sensors 50a and 50b and the refrigerant temperature detected by the refrigerant temperature sensors 55a and 55b, and the CPU 110a, 110b calculates | requires a refrigerant | coolant supercooling degree regularly (for example, every 30 second), and adjusts the opening degree of the 1st outdoor expansion valves 40a and 40b and the 2nd outdoor expansion valves 41a and 41b.

  As described above, according to the air conditioner of the present invention, the outdoor heat exchanger functions as an evaporator, that is, when the outdoor unit side refrigerant temperature detected during the heating operation or the heating main operation is performed. By comparing the indoor unit side refrigerant temperature with the liquid pipe, it is determined whether or not the liquid refrigerant is staying in the liquid pipe, and if it is determined that the liquid refrigerant is staying in the liquid pipe, the flow rate adjustment provided in the liquid pipe By increasing the opening degree of the means by a predetermined change amount, the liquid refrigerant staying in the liquid pipe can flow to the outdoor heat exchanger side. Thereby, it can prevent that a condensation capacity falls by an indoor heat exchanger by filling a liquid refrigerant with a liquid pipe, and can suppress the shortage of the heating capacity in the indoor unit which is performing heating operation.

  In the embodiment described above, an air conditioner that can perform an air-conditioning-free operation in which five indoor units are connected in parallel to two outdoor units with a high-pressure gas pipe, a low-pressure gas pipe, and a liquid pipe is taken as an example. Although described, a plurality of indoor units are connected to at least one outdoor unit in parallel by gas pipes and liquid pipes, and the present invention is also applied to a multi-type air conditioner that can perform cooling operation or heating operation simultaneously in all indoor units. Can do.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 2a, 2b Outdoor unit 6a-6e Switching unit 8a-8e Indoor unit 21a, 21b Compressor 22a, 22b 1st three-way valve 23a, 23b 2nd three-way valve 24a, 24b 1st outdoor heat exchanger 25a, 25b Second outdoor heat exchanger 26a, 26b Outdoor fan 27a, 27b Accumulator 28a, 28b Oil separator 29a, 29b Receiver tank 40a, 40b First outdoor expansion valve 41a, 41b Second outdoor expansion valve 51a, 51b Low pressure sensor 52a, 52b Intermediate Pressure sensor 55a, 55b Refrigerant temperature sensor 56a, 56b First heat exchange temperature sensor 57a, 57b Second heat exchange temperature sensor 58a, 58b Outside air temperature sensor 81a-81e Indoor heat exchanger 84a-84e Refrigerant temperature sensor 100a, 100b Control means 110a, 110b CP U
Toe Outdoor unit side refrigerant temperature Tif Indoor unit side refrigerant temperature Δt Differential temperature

Claims (3)

A compressor, an outdoor heat exchanger, and a flow path switching unit that is connected to one refrigerant inlet / outlet of the outdoor heat exchanger and switches the connection of the outdoor heat exchanger to a refrigerant discharge port or a refrigerant suction port of the compressor And a flow rate adjusting means connected to the other refrigerant inlet / outlet of the outdoor heat exchanger to adjust the flow rate of refrigerant in the outdoor heat exchanger, and a control means for controlling the flow path switching means and the flow rate adjusting means. At least one outdoor unit comprising:
A plurality of indoor units connected to the outdoor unit by one liquid pipe and at least one gas pipe, and provided with an indoor heat exchanger;
An air conditioner comprising:
The flow rate adjusting means and the indoor heat exchanger are connected by the liquid pipe,
On the flow rate adjusting means side in the liquid pipe, an outdoor unit side refrigerant temperature detecting means is provided on the refrigerant inflow side of the outdoor heat exchanger when the outdoor heat exchanger functions as an evaporator,
On the indoor heat exchanger side of the liquid pipe, an indoor unit side refrigerant temperature detection means is provided on the refrigerant outflow side of the indoor heat exchanger when the indoor heat exchanger functions as a condenser,
The control means controls the flow path switching means to cause the outdoor heat exchanger to function as an evaporator, and the outdoor unit side refrigerant temperature taken in from the outdoor unit side refrigerant temperature detection means and the indoor unit If the temperature difference with the indoor unit side refrigerant | coolant temperature taken in from the side refrigerant | coolant temperature detection means is less than predetermined value, the opening degree of the said flow volume adjustment means will be enlarged by the predetermined | prescribed change amount, The air conditioning apparatus characterized by the above-mentioned. The air conditioner according to claim 1,
When the temperature difference between the outdoor unit side refrigerant temperature and the indoor unit side refrigerant temperature is within a predetermined value, the control unit opens the flow rate adjusting unit according to the degree of refrigerant superheat in the outdoor heat exchanger. When the degree of change in the degree of opening of the flow rate adjusting means determined corresponding to the degree of refrigerant superheat is greater than the predetermined amount of change, the change determined corresponding to the degree of refrigerant superheat An air conditioner characterized in that the opening degree of the flow rate adjusting means is increased by an amount. The air conditioner according to claim 1,
The outdoor unit is provided with a discharge temperature detecting means for detecting a discharge temperature which is a temperature of the refrigerant discharged from the compressor,
The control means corresponds to the flow rate adjusting means corresponding to the discharge temperature detected by the discharge temperature detecting means when a temperature difference between the outdoor unit side refrigerant temperature and the indoor unit side refrigerant temperature is within a predetermined value. When the opening degree of the flow rate is controlled, if the change amount of the opening degree of the flow rate adjusting means determined corresponding to the discharge temperature is larger than the predetermined change amount, the change determined corresponding to the discharge temperature An air conditioner characterized in that the opening degree of the flow rate adjusting means is increased by an amount.

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