JP2015148387A - Air conditioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioning device capable of being operated at a discharge temperature lower than a compressor heatproof temperature and at a discharge temperature at which excess performance deterioration does not occur, and controlling an expansion valve capable of coping with discharge temperature change due to a load.SOLUTION: When a theoretical discharge temperature exceeds a target discharge temperature upper limit value and the difference therebetween is made large, an air conditioning device controls the opening of an expansion valve 27 so as to make it large in an opened direction, and controls the opening of the expansion valve 27 so as to make it small in the opened direction when the difference between the theoretical discharge temperature and a threshold is made small.

Description

  The present invention relates to an air conditioner, and more particularly to expansion valve control for improving cooling capacity and heating capacity.

  Conventionally, discharge temperature control of an expansion valve is performed in order to improve the operating performance and efficiency of the air conditioner or to maintain the reliability of the compressor. The discharge temperature control of the expansion valve means that the target discharge temperature is predicted from the condensation pressure and evaporation pressure of the refrigeration cycle so that the state of the refrigerant sucked in the compressor is optimal, and the expansion is performed so that the current discharge temperature becomes the target discharge temperature. The valve is controlled (hereinafter, feedback opening degree control) (for example, Patent Document 1).

  In Patent Document 1, the discharge temperature at which the evaporator outlet dryness = 1 is set as the optimum target discharge temperature. On the other hand, when a refrigerant having a warming coefficient smaller than that of R22 or R410A such as R32 and having a high adiabatic compression index is used for an air conditioner, the discharge temperature of the refrigerant is likely to be higher than in the past. On the other hand, in the compressor, when the internal motor winding exceeds the heat resistance temperature, the insulating portion is deteriorated or burned out. Therefore, even if the target discharge temperature is calculated and the feedback opening degree control is performed as in Patent Document 1, the upper limit temperature of the compressor is a problem, and the target discharge temperature cannot actually be set higher than the heat resistance temperature of the motor winding. Therefore, if the calculated target discharge temperature is used as it is, a protective operation for suppressing the discharge temperature to the heat resistant temperature or less often occurs, and stable operation is hindered.

 Here, in setting the target discharge temperature, it is necessary to set the temperature lower than the heat resistant temperature in order to avoid failure of the compressor. In this case, an operation (hereinafter referred to as a wet operation) is performed in which a temperature (evaporator outlet dryness <1) lower than a normal target discharge temperature (evaporator outlet dryness = 1) is set as a target value. At this time, if an operation that excessively lowers the discharge temperature is performed, the refrigerant that has not been sufficiently heat-exchanged by the evaporator is sucked into the compressor, and the heat exchange amount of the evaporator is reduced. As a result, the cooling capacity and heating capacity of the air conditioner are reduced. In addition, when the wet operation is excessive, the compressor sucks the liquid refrigerant and compresses the liquid refrigerant, which causes a failure. Therefore, it is necessary to operate at a temperature as high as possible in order to prevent performance degradation and compressor failure.

  As means for operating at a discharge temperature as high as possible while performing a wet operation, there is rotation speed pulse control of an expansion valve. The rotation speed pulse control of the expansion valve is control performed in a transition period in which the target discharge temperature changes, such as when the rotation speed of the compressor changes, such as at the start of operation. In the feedback opening degree control described above, the opening degree control is performed based on the actual discharge temperature. However, the actual discharge temperature has poor followability to changes in the rotation speed of the compressor. On the other hand, the rotational speed pulse control is a control method for predicting a change in the discharge temperature from a change in the rotational speed of the compressor and adjusting the opening of the expansion valve. As a result, even when the target discharge temperature changes due to a change in the rotational speed of the compressor during operation near the heat resistant temperature of the compressor, the expansion valve can be controlled by predicting the change in the target discharge temperature. It is possible to prevent the discharge temperature from exceeding the heat resistance temperature.

  However, the target discharge temperature of the compressor varies depending not only on the rotational speed of the compressor but also on the load (air temperature, room temperature, air volume, etc.). The above-described rotation speed pulse control can cope with changes in the target discharge temperature due to changes in the rotation speed of the compressor, but it can cope with changes in the target discharge temperature due to other factors (loads) that do not involve changes in the rotation speed of the compressor. Can not. Therefore, if the target discharge temperature changes due to the load during operation near the heat resistant temperature of the compressor, the heat resistant temperature may be exceeded, which hinders stable operation of the air conditioner. In some cases, the compressor may break down. In R22, R410A, etc., the target discharge temperature optimum for the refrigeration cycle was lower than the heat resistance temperature of the conventional compressor. Therefore, in R22, R410A, etc., it was not necessary to perform an operation for maintaining the discharge temperature at a high temperature near the heat resistant temperature of the compressor. Therefore, the risk that the discharge temperature exceeds the heat-resistant temperature during operation is low, and it is not necessary to consider the influence of load fluctuations. However, a refrigerant with a high adiabatic compression index such as R32 is required to operate stably at a temperature close to the heat-resistant temperature in order to bring out the performance of the air conditioner using R32, and the compression at the same heat-resistant temperature as before is required. When the machine is used, there is a high risk that the discharge temperature exceeds the heat resistance temperature during the operation of the air conditioner. Therefore, when a refrigerant with a high adiabatic compression index such as R32 is used, it is necessary to control the opening of the expansion valve in consideration of the influence of load fluctuation.

JP 54-49661 A

  The present invention was made to solve such problems, and in an air conditioner using a refrigerant with a high adiabatic compression index, the discharge temperature is lower than the heat resistant temperature of the compressor and the air conditioning capacity is excessively lowered. It is an object of the present invention to provide an air conditioner that can be operated at a discharge temperature that does not cause a discharge, and that controls an expansion valve that can cope with a change in discharge temperature due to load fluctuations.

  An air conditioner of the present invention includes a compressor, a condenser, an expansion valve, an evaporator, a condensation temperature sensor that detects a condensation temperature in the condenser, and an evaporation temperature sensor that detects an evaporation temperature in the evaporator. And a discharge temperature sensor for detecting a refrigerant discharge temperature from the compressor, and when the refrigerant sucked into the compressor determined in advance based on the condensation temperature and the evaporation temperature is dryness = 1 Feedback opening degree control that controls the opening degree of the expansion valve so that the refrigerant discharge temperature approaches the theoretical discharge temperature that is the temperature of refrigerant discharged from the compressor, and the refrigerant discharge temperature exceeds the heat resistant temperature of the compressor. An air conditioner that performs compressor protection stop control for stopping the operation of the compressor when the air conditioner has a target discharge temperature upper limit that is set in advance lower than the heat-resistant temperature. Temperature exceeded In addition, in addition to the feedback opening degree control, wetness control is performed to open the opening degree of the expansion valve in accordance with the magnitude of the temperature difference between the theoretical discharge temperature and the target discharge temperature upper limit value. Yes.

  2. The air conditioner according to claim 1, wherein the wetness control is a control for opening the expansion valve in an opening direction as a temperature difference between the theoretical discharge temperature and the target discharge temperature upper limit value increases. It is characterized by adjusting the amount addition rate to be large.

  Further, in the air conditioner according to claim 1 or 2, R32 is used as the refrigerant.

  According to the present invention, since it is possible to cope with a change in discharge temperature that does not accompany changes in the rotational speed of the compressor, the discharge temperature does not exceed the heat resistance temperature of the compressor, and the cooling capacity and heating capacity of the air conditioner are reduced. It is possible to stably operate at a discharge temperature with suppressed.

It is the schematic which shows the whole refrigerating cycle of the air conditioning apparatus of this embodiment. It is a figure which shows the comparison of the theoretical discharge temperature of R32 and R410A. It is a figure which shows the change of the wet level according to the difference of the target discharge temperature upper limit of this embodiment, and theoretical discharge temperature. It is the figure which showed the relationship between the change of the wet level of this embodiment, and a pulse addition rate. It is a flowchart which shows the opening degree control of the expansion valve of the air conditioning apparatus of a present Example. It is a flowchart which shows the initial stage pulse control and rotation speed pulse control of the air conditioning apparatus of a present Example. It is a flowchart which shows the feedback opening degree control of the air conditioning apparatus of a present Example. It is a flowchart which shows the wetness control of the air conditioning apparatus of a present Example.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 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. 1A, an air conditioner 1 according to this embodiment includes an outdoor unit 2 installed outdoors, and an indoor unit 3 connected to the outdoor unit 2 with a liquid pipe 4 and a gas pipe 5. I have. Specifically, the liquid pipe 4 has one end connected to the closing valve 25 of the outdoor unit 2 and the other end connected to the liquid pipe connecting portion 34 of the indoor unit 3. The gas pipe 5 has one end connected to the closing valve 26 of the outdoor unit 2 and the other end connected to the gas pipe connecting portion 35 of the indoor unit 3. The refrigerant circuit 10 of the air conditioner 1 is configured as described above.

  First, the outdoor unit 2 will be described. The outdoor unit 2 includes a compressor 20, a four-way valve 22, an outdoor heat exchanger 23, a closing valve 25 to which one end of the liquid pipe 4 is connected, a closing valve 26 to which one end of the gas pipe 5 is connected, An accumulator 21 and an outdoor fan 24 are provided. And these each apparatus except the outdoor fan 24 is mutually connected by each refrigerant | coolant piping explained in full detail below, and the outdoor unit refrigerant circuit 10a which makes a part of the refrigerant circuit 10 is comprised.

  The compressor 20 is a variable-capacity compressor that can vary the operation capacity by being driven by a motor 201 whose rotational speed is controlled by an inverter (not shown). The refrigerant discharge side of the compressor 20 is connected to the port a of the four-way valve 22 by a discharge pipe 61, and the refrigerant suction side of the compressor 20 is connected to the refrigerant outflow side of the accumulator 21 by a suction pipe 66. Yes.

  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. The port a is connected to the refrigerant discharge side of the compressor 20 by the discharge pipe 61 as described above. The port b is connected to one refrigerant inlet / outlet of the outdoor heat exchanger 23 by a refrigerant pipe 62. The port c is connected to the refrigerant inflow side of the accumulator 21 by a refrigerant pipe 65. The port d is connected to the shutoff valve 26 and the outdoor unit gas pipe 64.

  The outdoor heat exchanger 23 exchanges heat between the refrigerant and the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 24 described later. As described above, one refrigerant inlet / outlet of the outdoor heat exchanger 23 is connected to the port b of the four-way valve 22 by the refrigerant pipe 62, and the other refrigerant inlet / outlet is connected to the closing valve 25 by the outdoor unit liquid pipe 63.

  The expansion valve 27 is provided in the outdoor unit liquid pipe 63. The expansion valve 27 is an electronic expansion valve. A detailed description of the opening degree control of the expansion valve 27 will be described later.

  The outdoor fan 24 is formed of a resin material and is disposed in the vicinity of the outdoor heat exchanger 23. The outdoor fan 24 is rotated by a fan motor (not shown) to take outside air into the outdoor unit 2 from a suction port (not shown), and the outdoor air exchanged heat with the refrigerant in the outdoor heat exchanger 23 from the blower outlet (not shown) to the outside of the outdoor unit 2. To release.

  As described above, in the accumulator 21, the refrigerant inflow side is connected to the port c of the four-way valve 22 by the refrigerant pipe 65, and the refrigerant outflow side is connected to the refrigerant intake side of the compressor 20 by the intake pipe 66. The accumulator 21 separates the refrigerant flowing into the accumulator 21 from the refrigerant pipe 65 into a gas refrigerant and a liquid refrigerant and causes the compressor 20 to suck only the gas refrigerant.

  In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1A, the discharge pipe 61 is provided with a discharge temperature sensor 73 that detects the temperature of the refrigerant discharged from the compressor 20.

  The outdoor heat exchanger 23 is provided with an outdoor heat exchanger temperature sensor 75 for detecting the temperature of the refrigerant flowing out of the outdoor heat exchanger 23 or flowing into the outdoor heat exchanger 23. An outdoor air temperature sensor 76 that detects the temperature of the outside air flowing into the outdoor unit 2, that is, the outside air temperature, is provided in the vicinity of a suction port (not shown) of the outdoor unit 2.

  Further, the outdoor unit 2 is provided with an outdoor unit control means 100. The outdoor unit control means 100 is mounted on a control board stored in an electrical component box (not shown) of the outdoor unit 2. As shown in FIG. 1B, the outdoor unit control means 100 includes a CPU 110, a storage unit 120, a communication unit 130, a detection value input unit 140, and an expansion valve control unit 150.

  The storage unit 120 includes a ROM and a RAM, and stores a control program for the outdoor unit 2, detection values corresponding to detection signals from various sensors, control states of the compressor 20 and the outdoor fan 24, and the like. The communication unit 130 is an interface for performing communication with the indoor unit 3. The detection value input unit 140 captures detection results from various sensors of the outdoor unit 2 and outputs them to the CPU 110. The expansion valve control unit 150 controls the opening degree of the expansion valve 27 described later.

  The CPU 110 takes in the detection results of the various sensors of the outdoor unit 2 described above via the detection value input unit 140. Further, the CPU 110 takes in a control signal transmitted from the indoor unit 3 via the communication unit 130. In addition, the CPU 110 performs drive control of the compressor 20 and the outdoor fan 24 based on the detection results and control signals taken in. Furthermore, the CPU 110 performs switching control of the four-way valve 22 based on the acquired detection result and control signal.

  Next, the indoor unit 3 will be described with reference to FIG. The indoor unit 3 includes an indoor heat exchanger 31, a liquid pipe connection part 34 to which the other end of the liquid pipe 4 is connected, a gas pipe connection part 35 to which the other end of the gas pipe 5 is connected, an indoor fan 33, It has. And these each apparatus except the indoor fan 33 is mutually connected by each refrigerant | coolant piping explained in full detail below, and the indoor unit refrigerant circuit 10b which comprises a part of refrigerant circuit 10 is comprised.

  The indoor heat exchanger 31 exchanges heat between the refrigerant and indoor air taken into the indoor unit 3 from a suction port (not shown) by an indoor fan 33 to be described later, and one refrigerant inlet / outlet is connected to the liquid pipe connecting portion 34. The other refrigerant inlet / outlet is connected to the gas pipe connecting portion 35 via the indoor unit gas pipe 69. The indoor heat exchanger 31 functions as an evaporator when the indoor unit 3 performs a cooling operation, and functions as a condenser when the indoor unit 3 performs a heating operation. In addition, in the liquid pipe connection part 34 and the gas pipe connection part 35, each refrigerant | coolant piping is connected by welding, a flare nut, etc.

  The indoor fan 33 is formed of a resin material and is disposed in the vicinity of the indoor heat exchanger 31. The indoor fan 31 is rotated by a fan motor (not shown) so that indoor air is taken into the indoor unit 3 from a suction port (not shown), and the indoor air heat exchanged with the refrigerant in the indoor heat exchanger 31 is sent from the blower outlet (not shown) to the room. Blow out.

In addition to the configuration described above, the indoor unit 3 is provided with various sensors. The indoor heat exchanger 31 is provided with an indoor heat exchanger temperature sensor 78 that detects the temperature of the refrigerant passing through the indoor heat exchanger 31. An indoor temperature sensor 79 for detecting the temperature of the indoor air flowing into the indoor unit 3, that is, the indoor temperature is provided near the suction port (not shown) of the indoor unit 3.

  Next, the flow of the refrigerant and the operation of each part in the refrigerant circuit 10 during the air conditioning operation of the air conditioner 1 in the present embodiment will be described with reference to FIG. In the following description, the case where the indoor unit 3 performs the cooling operation will be described, and the detailed description of the case where the indoor operation 3 performs the heating operation will be omitted. Moreover, the arrow in FIG. 1 (A) has shown the flow of the refrigerant | coolant at the time of air_conditionaing | cooling operation.

  As shown in FIG. 1 (A), when the indoor unit 3 performs a cooling operation, the outdoor unit control means 100 is in a state where the four-way valve 22 is indicated by a solid line, that is, the port a and the port b of the four-way valve 22 communicate with each other. In addition, switching is performed so that port c and port d communicate with each other. Thereby, the outdoor heat exchanger 23 functions as a condenser, and the indoor heat exchanger 31 functions as an evaporator.

  The high-pressure refrigerant discharged from the compressor 20 flows through the discharge pipe 61 and flows into the four-way valve 22, and flows from the four-way valve 22 through the refrigerant pipe 62 and flows into the outdoor heat exchanger 23. The refrigerant flowing into the outdoor heat exchanger 23 is condensed by exchanging heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 24. The refrigerant flowing out of the outdoor heat exchanger 23 flows through the outdoor unit liquid pipe 63 and is reduced in pressure when passing through the expansion valve 27 to become a low-pressure refrigerant. Thereafter, the liquid flows into the liquid pipe 4 through the closing valve 25.

  The refrigerant flowing through the liquid pipe 4 and flowing into the indoor unit 3 through the liquid pipe connecting portion 34 flows through the indoor unit liquid pipe 68, flows into the indoor heat exchanger 31 from the indoor unit liquid pipe 68, and flows into the indoor fan 33. It evaporates by exchanging heat with the indoor air taken into the interior of the indoor unit 3 by rotation. As described above, the indoor heat exchanger 31 functions as an evaporator, and the indoor heat exchanger 31 performs heat exchange with the refrigerant to cool the indoor air, which is then blown into the room through a blowout port (not shown), whereby the indoor unit 3 Cooling of the room where is installed.

The refrigerant flowing out of the indoor heat exchanger 31 flows through the indoor unit gas pipe 69 and flows into the gas pipe connecting portion 35 gas pipe 5. Refrigerant flowing through the gas pipe 5 and flowing into the outdoor unit 2 through the shut-off valve 26 sequentially flows through the outdoor unit gas pipe 64, the four-way valve 22, the refrigerant pipe 65, the accumulator 21, and the suction pipe 66 and is sucked into the compressor 20. And compressed again.
As described above, the cooling operation of the air conditioner 1 is performed by circulating the refrigerant through the refrigerant circuit 10.

  When the indoor unit 3 performs the heating operation, the outdoor unit control means 100 is configured so that the four-way valve 22 is indicated by a broken line, that is, the port a and the port d of the four-way valve 22 communicate with each other. Switch so that port c communicates. Thereby, the outdoor heat exchanger 23 functions as an evaporator, and the indoor heat exchanger 31 functions as a condenser.

  Next, a method for controlling the expansion valve 27 will be described in detail.

  The expansion valve 27 is controlled to adjust the refrigerant circulation amount in the refrigerant circuit 10. The cooling / heating capacity is adjusted by adjusting the refrigerant circulation amount, and the proper refrigerant suction state of the compressor 20 is maintained. Thereby, the heat exchange efficiency of the evaporator (the outdoor heat exchanger 23 during heating and the indoor heat exchanger 31 during cooling) and the reliability of the compressor 20 can be improved.

  On the other hand, the compressor 20 includes the motor 201 inside as described above, and the winding of the motor 201 has a use upper limit temperature. If the winding exceeds the upper limit temperature, the insulation part may be deteriorated or burned out. Since the winding is exposed to the refrigerant on the discharge side in the compressor 20, in order to maintain the reliability of the compressor, it is necessary that the discharge temperature of the refrigerant does not become as high as the upper limit temperature of the winding. There is. Therefore, the storage unit 120 incorporates compressor protection control that stops the operation of the compressor 20 when the discharge temperature of the compressor 20 exceeds a predetermined temperature (heat-resistant temperature).

  The opening degree control of the expansion valve 27 is performed according to the required cooling or heating capacity. As a general control method, there is a control method in which the suction refrigerant of the compressor 20 is controlled to be dryness = 1. This is because if the refrigerant sucked into the compressor 20 is completely in a gas phase and further in a superheated state, the discharge temperature of the compressor 20 rises and the reliability is impaired. Further, even when the suction refrigerant of the compressor 20 has a dryness <1, the heat exchange efficiency in the evaporator decreases, and the liquid refrigerant that could not be evaporated by the compressor 20 is sucked and causes liquid compression. Therefore, the expansion valve is controlled with the target of the suction dryness = 1.

  The storage unit 120 of this embodiment incorporates a feedback opening degree control that controls the opening degree of the expansion valve 27 so that the discharge temperature of the compressor 20 approaches the theoretical discharge temperature (discharge temperature when the suction dryness = 1). It is out.

  The feedback opening degree control calculates a theoretical discharge temperature at which the dryness of the refrigerant sucked in the compressor is optimal (dryness = 1) from the condensation temperature and the evaporation temperature, and the detected discharge temperature approaches the theoretical discharge temperature. In this way, the control is to adjust the opening degree of the expansion valve 27. Specifically, when the temperature difference between the theoretical discharge temperature and the detected discharge temperature is large, the throttle amount of the opening is increased, and when the temperature difference is small, the throttle amount of the opening is decreased.

  At this time, the height of the theoretical discharge temperature range depends on the adiabatic compression index of the refrigerant. For example, R32 has a higher adiabatic compression index than R410A, so the theoretical discharge temperature is higher. Therefore, when R410A is used, the theoretical discharge temperature does not exceed the heat resistance temperature unless the operating condition is abnormal. Even when R32 is used, the theoretical discharge temperature is higher than the heat resistance temperature when R32 is used. It approaches or exceeds the heat resistance temperature. FIG. 2 shows a comparison between the temperature range (1) of the theoretical discharge temperature of R410A and the temperature range (2) of the theoretical discharge temperature of R32 when the same compressor is used. In R410A (1), the upper limit of the theoretical discharge temperature is d ° C. lower than the heat-resistant temperature b ° C. On the other hand, in R32 (2), the theoretical discharge temperature rises to a ° C. exceeding the heat resistance temperature b ° C.

  If the discharge temperature exceeds the heat resistance temperature, the compressor 20 is shut down due to compressor protection control. In order to avoid this, it is desirable to operate stably in a temperature range sufficiently lower than the heat-resistant temperature. On the other hand, the operation in which the discharge temperature becomes the theoretical discharge temperature (discharge temperature when the suction dryness = 1) is the optimum state. Therefore, even when the theoretical discharge temperature is a value close to or higher than the heat resistance temperature, there is a demand for stable operation at a high discharge temperature that is as close to the theoretical discharge temperature as possible. . If it demonstrates using FIG. 2, the driving | operation stabilized at c degree C close | similar to heat-resistant temperature b degree C is preferable. In this case, by stabilizing the theoretical discharge temperature in a temperature range lower than the heat-resistant temperature and close to the heat-resistant temperature, it is possible to suppress the performance degradation of the air conditioner 1 while maintaining the reliability of the compressor 20. However, since the condensation temperature and the evaporation temperature change due to an increase in the rotational speed of the compressor 20 and fluctuations in the load (room temperature and indoor air volume), the theoretical discharge temperature also changes accordingly, and the theoretical discharge temperature exceeds the heat resistance temperature. Sometimes. At this time, since the actual discharge temperature follows the theoretical discharge temperature in the feedback opening degree control, the actual discharge temperature exceeds the heat resistance temperature, and the compressor 20 stops. It is possible to solve this problem by raising the heat-resistant temperature of the compressor, but this leads to an increase in product cost.

  As described above, in an air conditioner using a refrigerant having a high adiabatic compression index, such as R32, that operates in a temperature range where the theoretical discharge temperature is close to the heat-resistant temperature, the theoretical discharge temperature changes due to load fluctuation or the like. However, a control that predicts the change and prevents the discharge temperature from exceeding the heat-resistant temperature has been desired. Therefore, the control of the present invention is performed.

  FIG. 5 is a flowchart showing a method for controlling the opening degree of the expansion valve 27 after the compressor 20 is started.

  First, after starting the compressor 20, initial pulse control is performed (ST1). Immediately after the compressor 20 starts up, the rotational speed of the compressor 20 increases toward the target rotational speed, the condensation temperature and evaporation temperature in the refrigeration cycle are not stable, and the theoretical discharge temperature cannot be calculated. Degree control is not possible. Instead, initial pulse control is performed in which the opening degree of the expansion valve 27 is adjusted in advance to an opening degree that can ensure an appropriate refrigerant flow rate. As a result, if the opening degree of the expansion valve 27 is insufficient when the rotation speed of the compressor 20 reaches the target value, the discharge temperature rises rapidly, and the heat resistant temperature is prevented from overshooting. When the initial pulse control is started, the initial pulse information is output from the storage unit 120 to the CPU 110 as shown in FIG. 6, and the CPU 110 transmits the acquired initial pulse information to the expansion valve 27 to control the opening (ST1). -1). Thereafter, the initial pulse control is terminated. The pulse is a control amount for controlling the opening degree of the expansion valve 27. When the pulse is added, the opening degree of the expansion valve 27 is controlled in the opening direction, and when subtracted, the opening degree of the expansion valve 27 is Controlled in the closing direction.

  Next, it is determined whether or not the target rotational speed (required rps) of the compressor 20 has changed (ST2). If there has been a change, rotational speed pulse control is performed (ST3). The rotation speed pulse control (ST3) will be described later. If there is no change in the rotational speed, it is determined whether or not a predetermined time t1 (minutes) has elapsed since the start of the compressor 20 (ST4). The predetermined time t1 is a preset time for the compressor 20 to reach the rotational speed requested by the outdoor unit control means 100. If the predetermined time has not elapsed, the process returns to ST2.

  Next, the rotation speed pulse control (ST3) will be described. This control is performed when there is a change in the rotational speed (rps) of the compressor 20. The detected discharge temperature (Td) has poor followability to changes in the theoretical discharge temperature (Tdi) in a short time. Therefore, in the feedback opening degree control performed based on the detected discharge temperature (Td), it takes time to stabilize the detected discharge temperature (Td), and the detected discharge temperature (Td) reaches the heat resistant temperature of the compressor 20. There is a case. Therefore, it is necessary to control the opening degree of the expansion valve 27 at the time when the refrigerant circulation amount changes. In this case, the opening degree control is performed in accordance with the change amount every time the rotation speed of the compressor 20 changes. In the rotational speed pulse control, as shown in FIG. 6, the rotational speed (rps) of the compressor 20 is detected (ST3-1), and the CPU 110 is predetermined according to the detected rotational speed (rps). The addition pulse is extracted from the storage unit 120 (ST3-2). Thereafter, the CPU 110 transmits information on the added addition pulse to the expansion valve 27 to perform opening degree control (ST3-3). Thereafter, the rotational speed pulse control is terminated.

  When the predetermined time t1 has elapsed since the start of the compressor start in ST4, the CPU 110 takes in the condensation temperature (Tc), the evaporation temperature (Te), the discharge temperature (Td), and the compressor rotation speed (rps) from the detection value input unit 140. (ST5). When the air conditioner 1 is in the heating operation, the outdoor heat exchanger 23 functions as an evaporator, and the indoor heat exchanger 31 functions as a condenser. Therefore, the detection value input unit 140 of the outdoor unit control means 100 determines the indoor heat exchanger temperature. The condensation temperature and evaporation temperature detected by the sensor 78 and the outdoor heat exchanger temperature sensor 75 are taken in and output to the CPU 110. Thereafter, the theoretical discharge temperature (Tdi) is calculated based on the condensation temperature (Tc), the evaporation temperature (Te), and the compressor rotational speed (rps) (ST6). After calculating the theoretical discharge temperature (Tdi), feedback (FB) opening degree control is performed (ST7).

  As described above, the feedback opening degree control is expanded so that the detected discharge temperature approaches the theoretical discharge temperature at which the dryness of the refrigerant sucked in the compressor is optimum (dryness = 1) from the condensation temperature and the evaporation temperature. This is control for adjusting the opening degree of the valve 27. First, as shown in FIG. 7, in the feedback opening degree control, it is determined whether a predetermined time t2 has elapsed since the previous feedback opening degree control (ST7-1). This predetermined time t2 is a control interval of feedback opening degree control, and it is also considered that t2 has elapsed even when it is the first feedback opening degree control after starting up the compressor 20. When the predetermined time t2 has not elapsed, the feedback opening degree control is terminated as it is, and when the predetermined time t2 has elapsed, the CPU 110 detects the discharge temperature (Td) detected in ST5 and the theoretical discharge temperature calculated in ST6 ( Tdi) difference (Tdx = Tdi−Td) is calculated, and an addition pulse predetermined according to the magnitude of the difference (Tdx) is extracted from the storage unit 120 (ST7-2). Thereafter, the CPU 110 transmits information on the added addition pulse to the expansion valve 27 to perform opening degree control (ST7-3). Then, feedback opening degree control is complete | finished.

  Thereafter, wetting control is performed (ST8). The reason why the theoretical discharge temperature (Tdi) changes in a short time is not only the change in the rotation speed (rps), but also the change due to the load variation such as the indoor air volume and room temperature. The opening degree control according to the rotation speed (rps) of the compressor 20 described above cannot cope with a change in the theoretical discharge temperature (Tdi) due to load fluctuation. Therefore, when the current discharge temperature (Td) is close to the heat resistant temperature, unnecessary compressor protection stop control may occur. In order to avoid this, predictive control for adjusting the opening degree of the expansion valve 27 in advance when the occurrence of a situation that requires adjustment of the opening degree of the expansion valve 27 is detected is necessary. Therefore, when the theoretical discharge temperature (Tdi) exceeds a certain threshold value, the opening degree of the expansion valve 27 is controlled to open in accordance with the magnitude of the difference from the threshold value. In the present embodiment, this is called wetness control.

  Next, a specific control mode of wetness control will be described in detail with reference to FIGS. 2, 3, 4, and 8.

In the wetness control, a threshold value called a target discharge temperature upper limit value (Tdl) that is lower than the heat-resistant temperature (points to b ° C. in FIG. 2) is set (points to c ° C. in FIG. 2). The wetting degree (wetting level) is calculated from the difference between Tdl) and the theoretical discharge temperature (Tdi) (ST8-1 in FIG. 8). The calculation method of the wet level (n) is:
n = (Tdi−Tdl) / d + 1 (when Tdi <Tdl, n = 0, otherwise n is an integer: rounded down to the nearest decimal place)
And At this time, d is the width of the wet level. For example, when d = 2 (FIG. 3), it means that the level changes every 2 ° C. FIG. 3 is a diagram showing the change in the wet level (n) according to the difference between the target discharge temperature upper limit (Tdl) and the theoretical discharge temperature (Tdi).

As shown in FIG. 3, when the difference (Tdx) between the target discharge temperature upper limit (Tdl) and the theoretical discharge temperature (Tdi) is increased, the wetness level when the difference exceeds 0, +2, +4, +6 (N) changes to I, II, III, and IV, respectively. When the wet level (n) changes, as shown in FIG. 4, a predetermined addition pulse corresponding to the changed wet level is taken out from the storage unit 120 (ST8-2 in FIG. 8). Thereafter, the CPU 110 transmits information of the added addition pulse to the expansion valve 27 to perform opening degree control (ST8-3 in FIG. 8). Thereafter, the wetness control is terminated. At this time, for example, when the wet level changes from 0 to I, the control pulse is added by 2%.
Further, in order to prevent hunting, hysteresis is provided at the time of ascent and descent (3 ° C.).

  According to the above-described wetting control, the opening degree of the expansion valve 27 can be adjusted according to the level of the wetting level even when the theoretical discharge temperature changes in a short time due to load fluctuation. Accordingly, the discharge temperature of the compressor 20 can be stabilized at a temperature lower than the heat resistant temperature and close to the heat resistant temperature, and the heating capacity and the cooling capacity of the air conditioner 1 can be maintained while maintaining the reliability of the compressor 20. Improvement can be achieved.

  In FIG. 5, after the wetting control (ST8) is finished, it is determined whether there is a command to stop the compressor 20 (ST9). If there is no command, the process returns to ST2 to perform the rotation speed pulse control, feedback opening degree control and wetting control. Follow each step. If there is a stop command, the compressor 20 is stopped.

  Further, in this embodiment, the wet level width is set to 2 ° C. and the hysteresis is set to 3 ° C. However, the embodiment of the present invention is not limited to this, and is appropriately set based on the test results and the like. In this embodiment, the pulse addition rate in FIG. 4 is also set to + 2% when the wet level increases from 0 to I, + 2% when the wet level increases from I to II, etc. Like the width and hysteresis, various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Outdoor unit 3 Indoor unit 4 Liquid pipe 5 Gas pipe 10 Refrigerant circuit 20 Compressor 201 Motor 21 Accumulator 22 Four-way valve 23 Outdoor heat exchanger 24 Outdoor fan 27 Expansion valve 31 Indoor heat exchanger 33 Indoor fan 61 Discharge Pipe 62 Refrigerant pipe 63 Outdoor air-liquid pipe 64 Outdoor unit gas pipe 65 Refrigerant pipe 66 Suction pipe 68 Indoor unit liquid pipe 69 Indoor unit gas pipe 73 Discharge temperature sensor 75 Outdoor heat exchanger temperature sensor 78 Indoor heat exchanger temperature sensor 79 Indoor Temperature sensor 100 outdoor unit control means

Claims (3)

 Compressor, condenser, expansion valve, evaporator, condensation temperature sensor for detecting the condensation temperature in the condenser, evaporation temperature sensor for detecting the evaporation temperature in the evaporator, and refrigerant discharge from the compressor A discharge temperature sensor for detecting temperature, and a temperature of the discharge refrigerant from the compressor when the intake refrigerant of the compressor determined in advance based on the condensation temperature and the evaporation temperature becomes dryness = 1 Feedback opening degree control for controlling the opening degree of the expansion valve so that the refrigerant discharge temperature approaches the theoretical discharge temperature, and the operation of the compressor when the refrigerant discharge temperature exceeds the heat resistant temperature of the compressor An air conditioner that performs compressor protection stop control for stopping the compressor, wherein the air conditioner performs feedback when the theoretical discharge temperature exceeds a target discharge temperature upper limit value that is set in advance lower than the heat-resistant temperature. In addition to the time control, the air conditioner which is characterized in that the wet control for opening control an opening degree of the expansion valve according to the magnitude of the temperature difference between the theoretical discharge temperature and the target discharge temperature limit. The wetness control is performed such that an addition rate of a control amount for controlling the opening degree of the expansion valve to increase is increased as a temperature difference between the theoretical discharge temperature and the target discharge temperature upper limit value increases. The air conditioning apparatus according to claim 1, wherein



  The air conditioner according to claim 1 or 2, wherein R32 is used as the refrigerant.

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