JP2018013301A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner capable of correctly determining whether or not frost formation is rapidly progressing in an outdoor heat exchanger. A CPU 210 determines whether or not a second frost formation condition is satisfied. Specifically, the CPU 210 reads out the heat exchange outlet temperature Too stored in the storage unit 220 in chronological order, determines whether or not the current heat exchange outlet temperature Too is equal to or lower than the second threshold temperature, and the latest heat exchange. Whether or not the rate of decrease in the heat exchange outlet temperature calculated using the outlet temperature Too and the previous heat exchange outlet temperature Too is equal to or higher than the predetermined rate of decrease, and while the two consecutive heat exchange outlet temperatures are stored in the room. It is determined whether the number of times the number of operating machines 5a to 5c has increased exceeds the predetermined number of times. Then, if the second frost formation condition is satisfied, the CPU 210 switches the four-way valve 22 to execute the defrosting operation preparatory process in which the refrigerant circuit 10 is used as the cooling cycle, and compresses when the defrosting operation preparatory process is completed. The machine 21 is restarted to start the defrosting operation. [Selection diagram] Fig. 1

Description

  The present invention relates to an air conditioner in which a plurality of indoor units are connected to an outdoor unit by refrigerant piping.

  When the air conditioner is performing a heating operation, the outdoor heat exchanger functioning as an evaporator may be frosted. When frost is formed on the outdoor heat exchanger, ventilation in the outdoor heat exchanger may be hindered by frost, and the heat exchange efficiency in the outdoor heat exchanger may be reduced. Therefore, when the outdoor heat exchanger is frosted, the heating operation is interrupted, the refrigerant circuit is switched so that the outdoor heat exchanger functions as a condenser, and the high-temperature refrigerant discharged from the compressor is transferred to the outdoor heat exchanger. There has been proposed an air conditioner that performs a defrosting operation to melt frost adhering to an outdoor heat exchanger by flowing (see, for example, Patent Document 1).

  In the air conditioning apparatus as described above, whether or not the outdoor heat exchanger is frosted during the heating operation is determined using the values detected by various temperature sensors provided in the outdoor unit and the duration of the heating operation. doing. For example, the heat exchange outlet temperature, which is the refrigerant temperature flowing out from the outdoor heat exchanger during the heating operation, is lower than −14 ° C., the temperature difference between the outside air temperature and the heat exchange outlet temperature is greater than 5 ° C., and the duration of the heating operation If it is in a state such as exceeding 3 hours, the defrosting operation is performed by determining that the amount of frost formation in the outdoor heat exchanger is at a level that hinders the heating capacity.

  On the other hand, when the outside air temperature during the heating operation is low and the outside air humidity is high, frost formation may suddenly progress in the outdoor heat exchanger (a large amount of frost adheres to the outdoor heat exchanger in a short time). Such a rapid progress of frost formation cannot be detected by the above-described method for determining the occurrence of frost formation. Therefore, it is conceivable to determine whether or not frosting is rapidly progressing in the outdoor heat exchanger by looking at whether or not the temperature of the outdoor heat exchanger is rapidly decreasing. For example, when the outlet temperature of the outdoor heat exchanger is detected periodically (for example, every 5 minutes) and the outlet temperature of the outdoor heat exchanger is lower than −6 ° C., the current outlet temperature of the outdoor heat exchanger is If the rate of decrease in the outlet temperature of the outdoor heat exchanger obtained by subtracting from the outlet temperature of the outdoor heat exchanger detected previously (5 minutes before) is greater than 2 ° C / 5 minutes, the outdoor heat exchanger suddenly forms frost. Is determined to be in progress, and the defrosting operation is executed.

  In an air conditioner in which a plurality of indoor units are connected to one outdoor unit, the number of indoor units that are operated during the heating operation may increase (the indoor unit that has been stopped until then starts the heating operation). . If the number of indoor units to be operated increases, the number of rotations of the compressor is increased according to the number of indoor units that have been increased. Even if it exists, it becomes large compared with the time of changing the normal required capacity (for example, when the set temperature is raised by 1 ° C. in the indoor unit). And if the rotation speed increase value of a compressor is large, the suction pressure of a compressor will fall large, and the exit temperature of an outdoor heat exchanger will also fall according to this. Accordingly, the number of indoor units operated is determined when it is determined whether or not frosting is rapidly progressing in the outdoor heat exchanger by looking at the rate of decrease in the outlet temperature of the outdoor heat exchanger described above during the heating operation. If it increases, the rate of decrease in the outlet temperature of the outdoor heat exchanger will increase in spite of the fact that frosting does not progress suddenly in the outdoor heat exchanger. There was a fear of being judged.

  On the other hand, the applicant first performed the heating operation in addition to the outlet temperature of the outdoor heat exchanger in the outdoor heat exchanger during the heating operation and the decrease rate of the outlet temperature of the outdoor heat exchanger. The air conditioning apparatus which judges the presence or absence of frost formation in consideration of whether the number of indoor units which have increased has been proposed (Japanese Patent Application No. 2015-042533). According to this, misjudgment of frost formation due to the increase in the number of operating units can be prevented.

JP 2009-228928 A

  However, if the increase in the number of operating indoor units is repeated, frosting may partially progress only near the entrance of the outdoor heat exchanger. In other words, the refrigerant distributed to the indoor units that were stopped immediately after the number of indoor units increased and the pipes connected to the indoor units did not flow but stayed there, and the refrigerant did not circulate immediately. There is a time difference between the refrigerant staying in the indoor unit that has been stopped after the number of rotations of the unit being increased and being sucked into the compressor. As a result, the pressure (low pressure) on the compressor suction side suddenly drops. At this time, the evaporation temperature also decreases. Since the temperature difference between the outdoor heat exchanger temperature and the outdoor air temperature increases, the refrigerant is heated from the middle of the flow path of the outdoor heat exchanger, and the temperature partially decreases from the inlet to the middle of the outdoor heat exchanger. To do. When this is repeated, frosting partially proceeds only near the entrance of the outdoor heat exchanger. In the case of the above-described conventional air conditioner (Japanese Patent Application No. 2015-042533), frost formation is not determined when the number of operating indoor units increases.

  The present invention solves the above-described problems, and provides an air conditioner that can determine without error whether or not frost formation has progressed in an outdoor heat exchanger due to an increase in the number of indoor units operated. The purpose is to do.

  In order to solve the above-described problems, the air conditioner of the present invention provides a temperature of refrigerant flowing out of the outdoor heat exchanger when the compressor, the four-way valve, the outdoor heat exchanger, and the outdoor heat exchanger function as an evaporator. An outdoor unit having a heat exchange outlet temperature detecting means for detecting the heat exchange outlet temperature and an outdoor air temperature detecting means for detecting the outside air temperature, a plurality of indoor units having an indoor heat exchanger, a compressor, a four-way valve, and the outdoor It has a refrigerant circuit in which a heat exchanger and a plurality of indoor heat exchangers are connected by refrigerant piping, and control means for controlling a compressor and a four-way valve. The control means performs the heating operation with the heat exchange outlet temperature detected by the heat exchange outlet temperature detecting means, the outside air temperature detected by the outside air temperature detecting means, and the heating operation when the refrigerant circuit is performing the heating operation with a plurality of indoor units. Regularly captures the number of indoor units in operation and stores them in time series. Then, if either one of the first frost condition and the second frost condition, which is a condition for frosting the outdoor heat exchanger, is satisfied, the control means switches the four-way valve to set the refrigerant circuit to the cooling cycle. A defrosting operation is performed to defrost the heat exchanger. Here, the first frost condition is whether the heat exchange outlet temperature is lower than the first threshold temperature, whether the duration of the heating operation is longer than a predetermined duration, or the outside air temperature and the heat exchange outlet. It includes at least one of whether or not the temperature difference is greater than the predetermined temperature difference. Further, the second frosting condition is whether or not the number of times the number of operating indoor units has increased is a predetermined number or more.

  Since the air conditioner of the present invention configured as described above determines whether or not the number of indoor units performing the heating operation during the heating operation is frosted, the number of indoor units operated is It can be judged without error whether or not frosting has progressed in the outdoor heat exchanger due to the increase.

It is explanatory drawing of the air conditioning apparatus which is embodiment of this invention, (A) is a refrigerant circuit figure, (B) is a block diagram of an outdoor unit control means. It is a flowchart explaining the process in the outdoor unit control means at the time of heating operation in embodiment of this invention.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. As an embodiment, an air conditioner will be described as an example in which three indoor units are connected to one outdoor unit in parallel through refrigerant pipes, and all the indoor units can simultaneously perform a cooling operation or a heating operation. 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 (A), the air conditioner 1 in the present embodiment includes one outdoor unit 2, and the outdoor unit 2 with a first liquid pipe 8a, a second liquid pipe 8b, a third liquid pipe 8c, And three indoor units 5 a to 5 c connected in parallel by the gas pipe 9.

  The above components are connected as follows. One end of the first liquid pipe 8a is connected to the first liquid side closing valve 27a of the outdoor unit 2, and the other end of the first liquid pipe 8a is connected to the liquid pipe connection portion 53a of the indoor unit 5a. One end of the second liquid pipe 8b is connected to the second liquid side closing valve 27b of the outdoor unit 2, and the other end of the second liquid pipe 8b is connected to the liquid pipe connection part 53b of the indoor unit 5b. One end of the third liquid pipe 8c is connected to the third liquid side closing valve 27c of the outdoor unit 2, and the other end of the third liquid pipe 8c is connected to the liquid pipe connection part 53c of the indoor unit 5c. One end of the gas pipe 9 is connected to the gas-side closing valve 28 of the outdoor unit 2, and the other end of the gas pipe 9 is branched and connected to the gas pipe connection portions 54a to 54c of the indoor units 5a to 5c. Thus, the outdoor unit 2 and the indoor units 5a to 5c are connected by the first liquid pipe 8a, the second liquid pipe 8b, the third liquid pipe 8c, and the gas pipe 9, and the refrigerant circuit 10 of the air conditioner 1 is connected. Is configured.

  The outdoor unit 2 includes a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, a first expansion valve 24a, a second expansion valve 24b, a third expansion valve 24c, an accumulator 25, and an outdoor fan 26. The first liquid side closing valve 27a, the second liquid side closing valve 27b, the third liquid side closing valve 27c, the gas side closing valve 28, and the outdoor unit control means 200 are provided. These devices other than the outdoor fan 26 and the outdoor unit control means 200 are connected to each other through refrigerant pipes described in detail below to form an outdoor unit refrigerant circuit 20 that forms part of the refrigerant circuit 10. Yes.

  The compressor 21 is a variable capacity compressor that can vary its operating capacity by being driven by a motor (not shown) whose rotational speed is controlled by an inverter. The refrigerant discharge port of the compressor 21 and the port a of the four-way valve 22 are connected by a discharge pipe 41, and the refrigerant suction side of the compressor 21 and the refrigerant outflow side of the accumulator 25 are connected by a suction pipe 42.

  The four-way valve 22 is a valve for switching the direction in which the refrigerant flows, and includes four ports a, b, c, and d. As described above, the port a and the refrigerant discharge port of the compressor 21 are connected by the discharge pipe 41. The refrigerant outlet 43 is connected to the port b and one refrigerant inlet / outlet of the outdoor heat exchanger 23. The port c and the refrigerant inflow side of the accumulator 25 are connected by a refrigerant pipe 46. The port d and the gas side closing valve 28 are connected by an outdoor unit gas pipe 45.

  The outdoor heat exchanger 23 exchanges heat between the outside air taken into the outdoor unit 2 through a suction port (not shown) and the refrigerant by the rotation of the outdoor fan 26. As described above, one refrigerant inlet / outlet of the outdoor heat exchanger 23 and the port b of the four-way valve 22 are connected by the refrigerant pipe 43. The other refrigerant inlet / outlet of the outdoor heat exchanger 23 and one end of each of the first liquid distribution pipe 44 a to the third liquid distribution pipe 44 c are connected by an outdoor unit liquid pipe 44. The outdoor heat exchanger 23 functions as a condenser when the refrigerant circuit 10 is in a cooling cycle, and functions as an evaporator when the refrigerant circuit 10 is in a heating cycle.

  The first expansion valve 24a is provided in the first liquid distribution pipe 44a. One end of the first liquid distribution pipe 44a is connected to the outdoor unit liquid pipe 44, and the other end is connected to the first liquid side closing valve 27a. The second expansion valve 24b is provided in the second liquid distribution pipe 44b. One end of the second liquid distribution pipe 44b is connected to the outdoor unit liquid pipe 44, and the other end is connected to the second liquid side shut-off valve 27b. The third expansion valve 24c is provided in the third liquid distribution pipe 44c. One end of the third liquid distribution pipe 44c is connected to the outdoor unit liquid pipe 44, and the other end is connected to the third liquid side closing valve 27c.

  The opening degrees of the first expansion valve 24a, the second expansion valve 24b, and the third expansion valve 24c are all controlled by the outdoor unit control means 200. The amount of refrigerant flowing through the indoor unit 5a is adjusted by controlling the opening of the first expansion valve 24a. By controlling the opening degree of the second expansion valve 24b, the amount of refrigerant flowing through the indoor unit 5b is adjusted. By controlling the opening of the third expansion valve 24c, the amount of refrigerant flowing through the indoor unit 5c is adjusted. The first expansion valve 24a, the second expansion valve 24b, and the third expansion valve 24c are electronic expansion valves driven by a pulse motor (not shown), and the opening degree is adjusted by the number of pulses given to the pulse motor.

  As described above, in the accumulator 25, the refrigerant inflow side and the port c of the four-way valve 22 are connected by the refrigerant pipe 46, and the refrigerant outflow side and the refrigerant suction port of the compressor 21 are connected by the suction pipe 42. The accumulator 25 separates the inflowing refrigerant into a gas refrigerant and a liquid refrigerant, and causes the compressor 21 to suck only the gas refrigerant through the suction pipe 42.

  The outdoor fan 26 is a propeller fan formed of a resin material disposed in the vicinity of the outdoor heat exchanger 23, and the outdoor fan 26 is rotated by a fan motor (not shown) so that the outdoor fan 2 is not shown. Outside air is taken into the interior of the outdoor unit 2 from the suction port, and the outside air heat-exchanged with the refrigerant flowing in the outdoor heat exchanger 23 is discharged to the outside of the outdoor unit 2 from a blower outlet (not shown) provided in the outdoor unit 2.

  In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1A, a discharge pipe 41 includes a high-pressure sensor 31 that detects the pressure of refrigerant discharged from the compressor 21, and a discharge temperature sensor that detects the temperature of refrigerant discharged from the compressor 21. 33 is provided. Near the refrigerant inflow side of the accumulator 25 in the refrigerant pipe 46, a low pressure sensor 32 that detects the pressure of the refrigerant sucked into the compressor 21, and a suction temperature sensor 34 that detects the temperature of the refrigerant sucked into the compressor 21. Is provided.

  In the vicinity of the outdoor heat exchanger 23 in the refrigerant pipe 43, there is a refrigerant that is a heat exchange outlet temperature detecting means for detecting the temperature of the refrigerant flowing out of the outdoor heat exchanger 23 when the outdoor heat exchanger 23 functions as an evaporator. A temperature sensor 35 is provided. The outdoor unit liquid pipe 44 is provided with a refrigerant temperature sensor 36 that detects the temperature of the refrigerant flowing into the outdoor heat exchanger 23 when the outdoor heat exchanger 23 functions as an evaporator. An outdoor air temperature sensor 37 that is an outside air temperature detecting means for detecting the temperature of the outside air flowing into the outdoor unit 2, that is, the outside air temperature, is provided near the suction port (not shown) of the outdoor unit 2.

  The outdoor unit 2 includes an outdoor unit control means 200. The outdoor unit control means 200 is mounted on a control board stored in an electrical component box (not shown) of the outdoor unit 2, and as shown in FIG. 1B, a CPU 210, a storage unit 220, a communication unit 230, The sensor input unit 240 is provided.

  The storage unit 220 includes a ROM and a RAM, and includes detection values corresponding to detection programs from the control program for the outdoor unit 2 and various sensors, driving states of the compressor 21 and the outdoor fan 26, and the indoor units 5a to 5c. The transmitted operation information of the indoor units 5a to 5c (including operation / stop information and set temperature information) is stored. The communication unit 230 is an interface that performs communication with the indoor units 5a to 5c. The sensor input unit 240 captures detection results from various sensors of the outdoor unit 2 and outputs them to the CPU 210. The CPU 210 periodically captures the detection values of various sensors via the sensor input unit 240 (for example, every 5 minutes), and also starts / stops the operation start / stop signal and operation information (set temperature) transmitted from the indoor units 5a to 5c. And an operation information signal including the room temperature are input via the communication unit 230. The CPU 210 controls the opening of the first expansion valve 24a to the third expansion valve 24c and the drive control of the compressor 21 and the outdoor fan 26 based on the various pieces of input information. Although not shown, the CPU 210 has a timer measurement function.

  Next, the three indoor units 5a to 5c will be described. The three indoor units 5a to 5c include indoor heat exchangers 51a to 51c, liquid pipe connection parts 53a to 53c, gas pipe connection parts 54a to 54c, and indoor fans 55a to 55c. And these apparatuses except indoor fan 55a-55c are mutually connected by each refrigerant | coolant piping explained in full detail below, and comprise the indoor unit refrigerant circuit 50a-50c which makes a part of refrigerant circuit 10. FIG.

  In addition, since the structure of all the indoor units 5a-5c is the same, in the following description, only the structure of the indoor unit 5a is demonstrated and description is abbreviate | omitted about the other indoor units 5b and 5c. In FIG. 1A, the configuration of the indoor units 5b and 5c corresponding to the configuration of the outdoor unit 5a is obtained by changing the end of the number given to the configuration of the indoor unit 5a from a to b and c. .

The indoor heat exchanger 51a exchanges heat between the refrigerant and indoor air taken into the indoor unit 5a from a suction port (not shown) provided in the indoor unit 5a by rotation of the indoor fan 55a. One refrigerant inlet / outlet of the indoor heat exchanger 51a and the liquid pipe connecting portion 53a are connected by an indoor unit liquid pipe 71a. The other refrigerant inlet / outlet of the indoor heat exchanger 51a and the gas pipe connecting portion 54a are connected by an indoor unit gas pipe 72a. Each refrigerant pipe is connected to the liquid pipe connecting portion 53a and the gas pipe connecting portion 54a by welding, a flare nut, or the like.
The indoor heat exchanger 51a functions as an evaporator when the indoor unit 5a performs a cooling operation, and functions as a condenser when the indoor unit 5a performs a heating operation.

  The indoor fan 55a is a cross-flow fan formed of a resin material disposed in the vicinity of the indoor heat exchanger 51a, and is rotated by a fan motor (not shown) to enter the indoor unit 5a from the suction port (not shown). Air is taken in and the indoor air heat-exchanged with the refrigerant in the indoor heat exchanger 51a is supplied to the room from an unillustrated air outlet provided in the indoor unit 5a.

  In addition to the configuration described above, the indoor unit 5a is provided with various sensors. The indoor unit liquid pipe 71a is provided with a liquid side temperature sensor 61a that detects the temperature of the refrigerant flowing into or out of the indoor heat exchanger 51a. The indoor unit gas pipe 72a is provided with a gas side temperature sensor 62a that detects the temperature of the refrigerant flowing out of the indoor heat exchanger 51a or flowing into the indoor heat exchanger 51a. An indoor temperature sensor 63a that detects the temperature of the indoor air flowing into the indoor unit 5a, that is, the indoor temperature, is provided near the suction port (not shown) of the indoor unit 5a.

  Next, when the air-conditioning apparatus 1 of the present embodiment performs the heating operation, and during the heating operation, any one of the first frost condition, the second frost condition, or the third frost condition described later is established. Then, for each of the defrosting operations, the refrigerant flow and the operation of each part in the refrigerant circuit 10 will be described with reference to FIG. In the following description, first, the refrigerant flow and the operation of each part in the refrigerant circuit 10 during the heating operation are described, and then the first frost condition, the second frost condition, and the third frost condition are described in detail. The refrigerant flow and the operation of each part in the refrigerant circuit 10 during the defrosting operation will be described later.

  In FIG. 1A, the solid arrow indicates the refrigerant flow during the heating operation, and the broken arrow indicates the refrigerant flow during the defrosting operation. However, since the refrigerant flow from the compressor 21 to the port a of the four-way valve 22 and the refrigerant flow from the port c of the four-way valve 22 to the compressor 21 are the same during the heating operation and the defrosting operation, the solid line Shown with arrows only. Moreover, about the four-way valve 22, the communication state between each port at the time of heating operation is shown with the continuous line, and the communication state between each port at the time of a defrost operation is shown with the broken line.

<Heating operation>
When the indoor units 5a to 5c perform the heating operation, that is, when the refrigerant circuit 10 is in the heating cycle, the CPU 210 of the outdoor unit control means 200 indicates the four-way valve 22 by a solid line as shown in FIG. The state is switched, that is, the port a and the port d of the four-way valve 22 communicate with each other, and the port b and the port c communicate with each other. Thereby, the outdoor heat exchanger 23 functions as an evaporator, and the indoor heat exchangers 51a to 51c function as condensers. Then, the CPU 210 activates the compressor 21 and the outdoor fan 26.

  When the compressor 21 is activated, the refrigerant circulates through the refrigerant circuit 10 as indicated by the solid line arrow shown in FIG. That is, the high-pressure refrigerant discharged from the compressor 21 flows into the four-way valve 22 from the discharge pipe 41, flows through the outdoor unit gas pipe 45 from the four-way valve 22, and flows into the gas pipe 9 through the gas side shut-off valve 28. . The refrigerant that has flowed into the gas pipe 9 is divided and flows into the indoor units 5a to 5c through the gas pipe connecting portions 54a to 54c. The refrigerant that has flowed into the indoor units 5a to 5c flows through the indoor unit gas pipes 72a to 72c, flows into the indoor heat exchangers 51a to 51c, and is taken into the indoor units 5a to 5c by the rotation of the indoor fans 55a to 55c. Heat exchanges with room air and condenses. As described above, the indoor heat exchangers 51a to 51c function as condensers, and the indoor air that has exchanged heat with the refrigerant in the indoor heat exchangers 51a to 51c is blown into the room from a blowout port (not shown), thereby The room where the machines 5a to 5c are installed is heated.

  The refrigerant that has flowed out of the indoor heat exchangers 51a to 51c flows through the indoor unit liquid pipes 71a to 71c, and flows into the first liquid pipe 8a to the third liquid pipe 8c via the liquid pipe connection portions 53a to 53c. The refrigerant flowing into the first liquid pipe 8a to the third liquid pipe 8c flows into the outdoor unit 2 via the first liquid side closing valve 27a to the third liquid side closing valve 27c, and the first liquid distribution pipes 44a to 3rd. When flowing through the liquid distribution pipe 44c, the pressure is reduced by passing through the first expansion valve 24a to the third expansion valve 24c.

  The refrigerant depressurized by each expansion valve flows into the outdoor unit liquid pipe 44 from the first liquid pipe 44a to the third liquid pipe 44c and joins, and then flows into the outdoor heat exchanger 23. The refrigerant flowing into the outdoor heat exchanger 23 evaporates by exchanging heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 26. The refrigerant that has flowed out of the outdoor heat exchanger 23 into the refrigerant pipe 43 flows through the refrigerant pipe 46 via the four-way valve 22, flows into the accumulator 25, and is separated into a gas refrigerant and a liquid refrigerant by the accumulator 25. The gas refrigerant flowing out of the accumulator 25 flows through the suction pipe 42 and is sucked into the compressor 21 and compressed again.

<Defrosting operation>
When the air conditioning apparatus 1 is performing the heating operation as described above, if any one of the first frost condition, the second frost condition, or the third frost condition described below is satisfied. The CPU 210 performs the defrosting operation for interrupting the heating operation and defrosting the outdoor heat exchanger 23.

  Here, the first frosting condition is a condition indicating that the amount of frosting in the outdoor heat exchanger 23 may be at a level that hinders the heating capacity. Specifically, a heat exchange outlet temperature that is a temperature detected by the refrigerant temperature sensor 35 during the heating operation and indicates the temperature of the outdoor heat exchanger 23 functioning as an evaporator is set to a first threshold temperature (for example, , −14 ° C.), or whether the temperature difference between the outside air temperature detected by the outside air temperature sensor 37 and the heat exchange outlet temperature is larger than a predetermined temperature difference (for example, 5 ° C.), Alternatively, it includes at least one of whether or not the duration of the heating operation is longer than a predetermined duration (for example, 3 hours). The CPU 210 periodically takes in the heat exchange outlet temperature detected by the refrigerant temperature sensor 35 and the outside air temperature detected by the outside air temperature sensor 37 via the sensor input unit 240 (for example, every 5 minutes), and takes in the heat exchange taken in. The outlet temperature and the outside air temperature are stored in the storage unit 220 in time series.

  On the other hand, the second frosting condition is not included in the first frosting condition or the third frosting condition described later, but indicates that frosting is partially progressing in the outdoor heat exchanger 23. It is. Specifically, whether or not the outside air temperature is lower than a predetermined temperature (for example, 5 ° C.) and after the air-conditioning apparatus 1 starts the heating operation or after the previous defrosting operation is finished, That is, the number of times the number of indoor units 5a to 5c is increased to a predetermined number (for example, 30 times) or more. The CPU 210 stores the number of times in the storage unit 220 when the number of operating indoor units 5a to 5c increases.

  On the other hand, the third frost condition is a condition indicating that there is a possibility that the frost amount in the outdoor heat exchanger 23 may rapidly reach a level that interferes with the heating capacity. Specifically, whether or not the heat exchange outlet temperature is higher than the first threshold temperature and lower than a predetermined second threshold temperature (for example, −6 ° C.) during the heating operation, and the current Whether or not the rate of decrease in the heat exchange outlet temperature obtained by subtracting the heat exchange outlet temperature from the previously detected (5 minutes before) heat exchange outlet temperature is greater than a predetermined rate of decrease (for example, 2 ° C / 5 minutes); It includes whether or not the number of indoor units 5a to 5c operating while storing two consecutive heat exchange outlet temperatures has increased. The number of operating units of the indoor units 5a to 5c is determined by the CPU 210 based on the operation / stop information included in the operating information of the indoor units 5a to 5c transmitted from the indoor units 5a to 5c stored in the storage unit 220 described above. Refer to and grasp. This operation / stop information is transmitted each time the indoor units 5a to 5c start or stop operation, and the CPU 210 updates the operation / stop information stored in the storage unit 220 each time it is received.

  When the outside air temperature during the heating operation is low and the humidity is high, frost formation suddenly proceeds in the outdoor heat exchanger 23 (a large amount of frost adheres to the outdoor heat exchanger 23 in a short time). In such a case, the determination based on the first frosting condition described above cannot determine whether or not the temperature of the outdoor heat exchanger 23 has rapidly decreased. Therefore, the rapid frosting in the outdoor heat exchanger 23 proceeds. Cannot be detected. Therefore, the rate of decrease in the heat exchange outlet temperature is calculated using the periodically detected heat exchange outlet temperature, whether the heat exchange outlet temperature is lower than the second threshold temperature and the rate of decrease in the heat exchange outlet temperature is predetermined. If it is determined whether or not the temperature of the outdoor heat exchanger 23 is drastically decreased by looking at whether or not it is larger than the decrease rate, it is determined whether or not frosting is rapidly progressing in the outdoor heat exchanger 23. can do.

  Further, if the number of indoor units operated during the heating operation of the air conditioner 1 increases, the rotational speed of the compressor 21 increases accordingly. At this time, the increase in the number of rotations of the compressor is such that when only one indoor unit is operated, when the normal required capacity is changed (for example, the set temperature is increased by 1 ° C. in the indoor units 5a to 5c). It will be larger than When the increase value of the rotation speed of the compressor 21 is large, the suction pressure of the compressor 21 is greatly decreased, and the heat exchange outlet temperature in the outdoor heat exchanger 23 is also greatly decreased accordingly. Therefore, when the number of indoor units operated increases when the rapid frost formation is detected using the rate of decrease in the heat exchange outlet temperature, the temperature of the outdoor heat exchanger 23 is suddenly increased. Although the rate of decrease in the heat exchange outlet temperature increases even though it has not decreased, there is a risk that it is erroneously determined that frosting has suddenly progressed in the outdoor heat exchanger 23.

  Therefore, as the above-described third frosting condition, in addition to whether the heat exchange outlet temperature is lower than the second threshold temperature and whether the rate of decrease in the heat exchange outlet temperature is greater than a predetermined decrease rate, the continuous 2 It is also seen whether or not the number of indoor units 5a to 5c operating during the storage of the two heat exchange outlet temperatures has increased. Thereby, even if the heat exchange outlet temperature is drastically decreased, if the number of operating units of the indoor units 5a to 5c is increased, for example, if one unit is increased, the rotational speed of the compressor 21 is increased due to the increase of the operating number. Even if the rate of decrease in the heat exchange outlet temperature is greater than the predetermined rate due to this, it is erroneously determined that the frosting has suddenly progressed in the outdoor heat exchanger 23 and the defrosting operation is started. To prevent you from doing.

  By the way, when the increase in the number of operating units of the indoor units 5a to 5c is repeated, frost formation may partially progress only near the entrance of the outdoor heat exchanger 23. That is, the refrigerant distributed to the indoor units that have been stopped immediately after the number of operating units of the indoor units 5a to 5c increases and the pipes connected to the indoor units 5a to 5c does not flow but stays there, and the refrigerant does not circulate immediately. Therefore, there is a time difference until the refrigerant that has stayed in the indoor unit that has been stopped since the rotation speed of the compressor is sucked into the compressor. As a result, the pressure (low pressure) on the suction side of the compressor 21 temporarily drops suddenly. At this time, the evaporation temperature also decreases. Since the temperature difference between the outdoor heat exchanger temperature and the outdoor air temperature becomes large, the refrigerant is overheated from the middle of the flow path of the outdoor heat exchanger 23, and the temperature is partially from the inlet to the middle of the outdoor heat exchanger 23. Decreases. If this is repeated, frosting partially proceeds only in the vicinity of the entrance of the outdoor heat exchanger 23. Even when frosting progresses in this way, the number of operating indoor units 5a to 5c is increasing, and therefore the defrosting operation cannot be started under the above-described third frosting condition.

  Therefore, in the present invention, as the second frosting condition described above, whether or not the outside air temperature is lower than a predetermined temperature, and after the air-conditioning apparatus 1 starts the heating operation or after the previous defrosting operation ends. It is seen whether the number of times the number of indoor units 5a to 5c in operation has increased is a predetermined number or more. Accordingly, when the number of operating units of the indoor units 5a to 5c increases to a predetermined number, for example, 30 times or more, the increase in the operating number of the indoor units 5a to 5c is repeated and frosting partially proceeds. It can be determined that the defrosting operation is started. As the predetermined number of times, the number of times that the progress of frosting has been confirmed by an experiment or the like is set in advance, but may be varied according to the detection value of the outside air temperature sensor 37 and the detection value of the outside air humidity sensor 38. In this case, the number of times is set low for high outside air temperature and high outside air humidity (conditions for increasing the absolute humidity), which are conditions that allow the outdoor heat exchanger 23 to easily form frost, and the number of times is set high for low outside air temperature and low outside air humidity.

  If the first frost condition, the second frost condition, or the third frost condition is satisfied, the CPU 210 interrupts the heating operation and performs the defrosting operation. The CPU 210 stops the compressor 21 and the outdoor fan 26, and as shown in FIG. 1A, the four-way valve 22 is indicated by a broken line, that is, the port a and the port b of the four-way valve 22 communicate with each other. The port c and the port d are switched so as to communicate with each other. Thereby, the outdoor heat exchanger 23 functions as a condenser, and the indoor heat exchangers 51a to 51c function as evaporators. Then, the CPU 210 restarts the compressor 21 while the outdoor fan 26 is stopped.

  When the compressor 21 is restarted, the refrigerant circulates through the refrigerant circuit 10 as indicated by a broken line arrow shown in FIG. That is, the high-pressure refrigerant discharged from the compressor 21 flows into the four-way valve 22 from the discharge pipe 41, flows through the refrigerant pipe 43 from the four-way valve 22, and flows into the outdoor heat exchanger 23. The refrigerant flowing into the outdoor heat exchanger 23 melts frost adhering to the outdoor heat exchanger 23 and flows out from the outdoor heat exchanger 23 to the outdoor unit liquid pipe 44. The refrigerant that has flowed into the outdoor unit liquid pipe 44 flows through the first expansion valve 24a to the third expansion valve 24c, which is diverted to the first liquid distribution pipe 44a to the third liquid distribution pipe 44c and fully opened, and is closed on the first liquid side. It flows into the first liquid pipe 8a to the third liquid pipe 8c through the valve 27a to the third liquid side closing valve 27c.

  The refrigerant that has flowed from the first liquid pipe 8a to the third liquid pipe 8c into the indoor units 5a to 5c through the liquid pipe connection portions 53a to 53c flows through the indoor unit liquid pipes 71a to 71c and the indoor heat exchangers 51a to 51c. It evaporates by exchanging heat with room air. Note that the indoor fans 55a to 55c are stopped during the defrosting operation. The refrigerant that has flowed out of the indoor heat exchangers 51a to 51c into the indoor unit gas pipes 72a to 72c flows into the gas pipe 9 through the gas pipe connection portions 54a to 54c, flows through the gas pipe 9, and passes through the gas side closing valve 28. Through the outdoor unit 2. The refrigerant that has flowed into the outdoor unit 2 flows through the outdoor unit gas pipe 45, the four-way valve 22, and the refrigerant pipe 46, flows into the accumulator 25, and is separated into a gas refrigerant and a liquid refrigerant by the accumulator 25. The gas refrigerant flowing out of the accumulator 25 flows through the suction pipe 42 and is sucked into the compressor 21 and compressed again.

  Next, processing executed by the CPU 210 when the air-conditioning apparatus 1 of the present invention performs the heating operation will be described using the flowchart shown in FIG. In the flowchart shown in FIG. 2, ST represents a process step, and the number following this represents a step number. In FIG. 2, the processing related to the present invention is mainly described, and other processing, for example, general control related to the air conditioner 1 such as control according to the operating condition instructed by the user during the heating operation. A description of such processing is omitted. Moreover, in the following description, the outdoor air temperature detected by the outdoor air temperature sensor 37 is To, the heat exchange outlet temperature detected by the refrigerant temperature sensor 35 is Teo, and the number of indoor units operating among the indoor units 5a to 5c. The operating number is Ni. Further, as the first frost condition, it is determined whether or not the heat exchange outlet temperature detected by the refrigerant temperature sensor 35 is equal to or lower than −14 ° C. which is the first threshold temperature. The threshold temperature is set to −6 ° C., and the predetermined decrease rate is set to 2 ° C./5 minutes.

  When CPU 210 starts the heating operation, it starts timer measurement (ST1). Next, CPU 210 determines whether or not a first predetermined time has elapsed since the start of timer measurement in ST1 (ST2). Here, the first predetermined time is obtained by performing a test or the like in advance and stored in the storage unit 220 until the temperature and pressure of the refrigerant in the refrigerant circuit 10 are stabilized after the heating operation is started. This is the time required for (for example, 10 minutes).

  If the first predetermined time has not elapsed (ST2-No), CPU 210 returns the process to ST2. If the first predetermined time has elapsed (ST2-Yes), the CPU 210 resets the timer (ST3), the outside air temperature To detected by the outside air temperature sensor 37 and the heat exchange outlet temperature Teo detected by the refrigerant temperature sensor 35. Is read via the sensor input unit 240, and the current number of operating units Ni of the indoor units 5a to 5c is read from the storage unit 220 (ST4). CPU210 memorize | stores the taken-out outside temperature To, the heat exchanger outlet temperature Teo, and the operation number Ni of the indoor units 5a-5c together in the memory | storage part 220, when processing of ST4 is performed.

  Next, CPU 210 determines whether or not the first frosting condition is satisfied (ST5). Specifically, the CPU 210 reads the heat exchange outlet temperature Teo captured in ST4 and stored in the storage unit 220, and determines whether or not the heat exchange outlet temperature Teo is −14 ° C. or lower.

  If the first frosting condition is satisfied (ST5-Yes), that is, if the heat exchange outlet temperature Teo is 5 ° C. or more lower than the outside air temperature To, the CPU 210 proceeds to ST12. If the first frosting condition is not satisfied (ST5-No), that is, if the heat exchange outlet temperature Teo is not -14 ° C. or lower, the CPU 210 starts timer measurement (ST6), and performs timer measurement in ST6. It is determined whether a second predetermined time has elapsed since the start (ST7). Here, the second predetermined time is an interval time for taking in the outside air temperature To detected by the outside air temperature sensor 37 and the heat exchange outlet temperature Teo detected by the refrigerant temperature sensor 35, and is 5 minutes here.

  If the second predetermined time has not elapsed (ST7-No), CPU 210 returns the process to ST7. If the second predetermined time has elapsed (ST7-Yes), the CPU 210 resets the timer (ST8), the outside air temperature To detected by the outside air temperature sensor 37 and the heat exchange outlet temperature Teo detected by the refrigerant temperature sensor 35. Is read via the sensor input unit 240, and the current number of operating units Ni of the indoor units 5a to 5c is read from the storage unit 220 (ST9). Also in this case, the CPU 210 stores the taken outside air temperature To, the heat exchange outlet temperature Teo, and the number of operating units Ni of the indoor units 5a to 5c together in the storage unit 220.

  Next, CPU 210 determines whether or not the third frosting condition is satisfied (ST10). Specifically, the CPU 210 reads the heat exchange outlet temperature Teo stored in the storage unit 220 in ST4 and ST9, and stores whether the heat exchange outlet temperature Teo stored in ST9 is −6 ° C. or less and stored in ST9. Whether the rate of decrease in the heat exchange outlet temperature calculated using the heat exchange outlet temperature Teo and the heat exchange outlet temperature Teo stored in ST4 is 2 ° C./5 minutes or more, and is stored in the storage unit 220 in ST4 and ST9. The number of operating units of the indoor units 5a to 5c is compared to determine whether or not the number of operating units of the indoor units 5a to 5c has increased. That is, it is determined whether or not the number of operating indoor units 5a to 5c has increased while storing two consecutive heat exchange outlet temperatures Teo.

  If the third frosting condition is not satisfied (ST10-No), that is, the heat exchange outlet temperature Teo is higher than −6 ° C., or the rate of decrease in the heat exchange outlet temperature is less than 2 ° C./5 minutes, or the indoor units 5a to 5a. If the number of operating units 5c has increased, CPU 210 determines whether or not the second frosting condition is satisfied (ST11). Specifically, in ST11, the CPU 210 determines whether or not the outside air temperature To stored in the storage unit 220 in ST9 has a predetermined value lower than 5 ° C., and the indoor units 5a to 5 stored in the storage unit 220 in ST4 and ST9. It is determined whether the number of times the number of operating units of the indoor units 5a to 5c has increased by 30 times or more by comparing the number of operating units 5c. It should be noted that the number of times the number of operating indoor units 5 a to 5 c has increased is integrated from the start of the heating operation of the air conditioner 1 or the previous defrosting operation, and stored in the storage unit 220. The If the second frosting condition is not satisfied (ST11-No), that is, if the number of operating units of the indoor units 5a to 5c has not increased 30 times or more, the CPU 210 returns the process to ST5. If the third frosting condition is established (ST10-Yes), that is, the heat exchange outlet temperature Teo is -6 ° C or lower, the rate of decrease in the heat exchange outlet temperature is 2 ° C / 5 minutes or higher, and the indoor units 5a to 5c. If the number of operating units has not increased, the CPU 210 executes a defrosting operation preparation process (ST12). Similarly, if the second frosting condition is established (ST11-Yes), that is, if the number of operating units 5a to 5c increased 30 times or more, the operating number of indoor units 5a to 5c. The CPU 210 determines that frosting has partially progressed and the CPU 210 executes a defrosting operation preparation process (ST12). The defrosting operation preparation process is a process performed by the CPU 210 when the refrigerant circuit 10 is switched to perform the defrosting operation. As described above, the CPU 210 stops the compressor 21 and the outdoor fan 26, and FIG. As shown in (A), the four-way valve 22 is switched to a state indicated by a broken line, that is, the port a and the port b of the four-way valve 22 communicate with each other and the port c and the port d communicate with each other. And CPU210 which finished the process of ST12 restarts the compressor 21, and starts defrost operation (ST13).

  Next, CPU 210 determines whether or not the defrosting operation end condition is satisfied (ST14). The defrosting operation end condition is, for example, when the heat exchange outlet temperature Teo taken during the defrosting operation is 10 ° C. or higher, or when 10 minutes or more have elapsed since the start of the defrosting operation in ST12. Thus, it is the conditions considered that all the frost adhering to the outdoor heat exchanger 23 was melted.

  If the defrosting operation termination condition is not satisfied (ST14-No), the CPU 210 returns the process to ST13 and continues the defrosting operation. If the defrosting operation termination condition is satisfied (ST14-Yes), the CPU 210 executes the heating operation resuming process (ST15). The heating operation restart process is a process performed by the CPU 210 when the refrigerant circuit 10 is switched to return from the defrosting operation to the heating operation. The CPU 210 stops the compressor 21 and then performs the process shown in FIG. Thus, the four-way valve 22 is switched to a state indicated by a solid line, that is, so that the port a and the port d of the four-way valve 22 communicate with each other and the port b and the port c communicate with each other. And CPU210 which finished the process of ST14 restarts the compressor 21 and the outdoor fan 26, restarts heating operation (ST16), and returns a process to ST1.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 2 Outdoor unit 5a-5c Indoor unit 21 Compressor 22 Four-way valve 23 Outdoor heat exchanger 35 Refrigerant temperature sensor 37 Outdoor temperature sensor 200 Outdoor unit control part 210 CPU
220 storage unit 240 sensor input unit

Claims (3)

Compressor, four-way valve, outdoor heat exchanger, and heat exchange outlet that detects a heat exchange outlet temperature that is a temperature of a refrigerant flowing out of the outdoor heat exchanger when the outdoor heat exchanger functions as an evaporator An outdoor unit having a temperature detection means and an outside temperature detection means for detecting the outside air temperature;
A plurality of indoor units having an indoor heat exchanger;
A refrigerant circuit in which the compressor, the four-way valve, the outdoor heat exchanger, and the plurality of indoor heat exchangers are connected by refrigerant piping;
Control means for controlling the compressor and the four-way valve;
An air conditioner comprising:
When the control means is performing a heating operation with the plurality of indoor units using the refrigerant circuit as a heating cycle,
The heat exchange outlet temperature detected by the heat exchange outlet temperature detection means, the outside air temperature detected by the outside air temperature detection means, and the number of indoor units operating in heating operation are periodically taken in time series. Remember with
If either the first frost condition or the second frost condition, which is a condition for generating frost in the outdoor heat exchanger, is satisfied, the four-way valve is switched to set the refrigerant circuit to a cooling cycle. Perform a defrosting operation to defrost the heat exchanger,
In the first frosting condition, the heat exchange outlet temperature is lower than a first threshold temperature, the duration of the heating operation is longer than a predetermined duration, or the outside air temperature and the heat Including at least one of whether the temperature difference of the outlet temperature is larger than the predetermined temperature difference,
The second frosting condition is whether or not the outside air temperature is lower than a predetermined temperature, and whether or not the number of operating units of the indoor unit has increased more than a predetermined number. The air conditioner according to claim 1, wherein the predetermined number of times is set such that a smaller value is set as the outside air temperature becomes higher. In addition to the first frost condition and the second frost condition, if any one of the third frost conditions, which is a condition for generating frost in the outdoor heat exchanger, is satisfied, the four-way valve is Switching and performing a defrosting operation to defrost the outdoor heat exchanger with the refrigerant circuit as a cooling cycle,
The third frosting condition is stored in time series as to whether or not the latest heat exchange outlet temperature is lower than a second threshold temperature higher than the first threshold temperature among the heat exchange outlet temperatures stored in time series. Whether or not the rate of decrease in the heat exchange outlet temperature calculated using the two consecutive heat exchange outlet temperatures out of the heat exchange outlet temperatures is greater than a predetermined reduction rate, and the two consecutive heat exchange outlet temperatures Including whether the number of operating indoor units has increased during storage,
The air conditioning apparatus according to claim 1 or 2, wherein

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